外堀の土塁 The Structure of the Outer Moat Ground 外堀土塁の構造 The Structure of the Base 牛込門から赤坂門までの江戸城外堀は、谷地形を利用し、広い堀幅の水面と、水面から高い土塁を持つ江戸城防御のための空間で構成されています。目の前に見える土手もその土塁の一部であり、2013（平成25）年から始まった石垣修復工事、その後のJR飯田橋駅西口駅舎等の工事に併せ調査が行われ、桝形石垣付近は江戸時代当時の規模を目安とした土塁の復元をしています。 外堀の土塁は、厚さ５～10cm程度ごとに土や粘土、砂など様々な種類の土を積み重ねて突き固められた版築と呼ばれる技法で作られています。地層断面をみると、土手の斜面方向とは逆に、水面の方に向かって地層が上がっています。これは、土砂崩れを防ぐためと考えられています。土塁の道路端には土留めの石垣が築かれていましたが、現在では土手に沿って通る道路の端に確認できる通り、コンクリートの小型擁壁に代わっています。
The section of Edo Castle’s outer moat between Ushigome and Akasaka Gates was constructed by utilizing the valley topography, which allowed for the development of a wide canal surface and tall earthwork fortifications. The embankment visible here formed a portion of the area’s earthen fortifications. In 2013, a series of excavations were carried out in conjunction with a project to repair the stone walls and redevelop the western side of JR Iidabashi Station. The project enabled the reconstruction of earthen fortifications on the same scale as those that existed in the Edo era. As a result, contemporary visitors to the site can experience the grand scale of the historical fortifications that existed in the area. The outer moat’s fortifications were constructed using a rammed-earth technique in which 5-to-10-centimeter layers of earth and clay were stacked on top of one another and tamped down. An examination of the fortifications geological profile reveals that the layers of earth and clay rise towards the towards the moat’s surface and away from the embankment slope, It is likely that this construction method was utilized in order to prevent landslides. Earth-reinforced stone walls were constructed along the roadside lining the earthen fortifications. However, as can be determined from the roadside currently located parallel to the embankment, the original earth-reinforced walls have been replaced by small-scale concrete retaining walls.
外堀土塁の水際部分（発見された水際石垣） Waterside Part of The Outer Moat Ground (Discovered Waterside Stone Wall 2015（平成27）年に行われた発掘調査の結果、外堀の水際には、土手が崩れないようにするための低い石垣が作られていたことが判明しました。発見された場所は、牛込橋から140m程度市谷方向に進む地点の線路の間で、石垣の基礎部分と考えられる 1〜2段の石積みが、外堀で初めて確認されました。この石垣は、明治期に甲武鉄道が敷設された際に、上段部分が撤去され、基礎部分はそのまま埋められたものと考えられます。
An archaeological excavation carried out in 2015 revealed the existence of low stone walls along the moat’s edge. They were likely constructed in order to prevent the embankment from collapsing into the moat. The site where the walls were discovered is located in a section of rail track approximately 140 meters away from Ushigome-bashi Bridge in the direction of Ichigaya. At that site, excavators found one- and two-tier layers of stone, which are thought to have comprised the stone walls’ structural foundation. When the Kōbu Railway was constructed in the Meiji period, it is thought that the upper portion of the stone walls were removed and the foundation was buried.
外堀土塁の植栽 Planting of The Outer Moat Earth Fence 1636（寛永13）年、外堀土塁が完成すると、幕府は翌年、堀方七組の東国大名に命じて、土塁上部から2.7m程下がった位置に、一間（約1.8m）間隔で大きめの松杉を、その内側には小さめの苗木を、二筋にわたって植樹させました。植木奉行（のち普請奉行）の管理下に置かれた牛込土橋～筋違橋の土手と堀は、近辺に屋敷を拝領する武家に割振り、植木の手入れと草刈りを担当させました。幕末に日本を訪れたオイレンブルクの『日本遠征記』によれば、「城壁天端の平坦部とその内側にはモミなどの針葉がぎっしりと並び、水面には何千という野鴨が住み着いている」と記されています。なお、真田濠（現上智大学グラウンド）の土塁上には、往時の姿を思い浮かべることができるような松の植生がみられます。
The outer moat’s earthenworks were completed in 1636. The following year, the Tokugawa shogunate order the group of eastern Japanese domainal lords previously mobilized to dig portions of the outer moat to plant a row of pine and cedar trees approximately 2.7 meters below the upper portion of those fortifications. The trees were to be planted 1.8 meters apart. In addition, they planted an inner row of smaller saplings parallel with the pine and cedar trees. This project was carried out under the direction of the Governor of Landscaping (later the Governor of Construction) and the maintenance of the newly planted fauna was entrusted to the warrior houses occupying estates along the outer moat and embankment between Ushigome-bashi Bridge and Kuichigai Gate. During the late-Edo period, the area was visited by Prussian diplomat Count Friedrich Albrecht zu Eulenburg. In his Record of the Eulenburg Expedition to Japan, he wrote, “Thick rows of fir trees and other conifers line the flat section crowning the castle walls and the walls’ interior section, and thousands of wild ducks inhabit the moats surface.” The rows of pine trees lining the embankment alongside Sanada-bori Moat (present-day Jōchi University Field) provide visitors with a sense of what the outer moat area was like in the Edo period.
Also known as the Ushigome Gateway, Ushigome-mon Gate was constructed in 1636 under the direction of Hasuchika Tadateru, the lord of Tokushima domain. As described in the Illustrated Maps of Edo Castle’s Outer Gates, Ushigome-mon Gate’s inner section was surrounded by stone walls, which were arranged in a square shape to form an enclosure. It was comprised of two gates: a Korean-style outer gate, which led to a square courtyard and could be entered from the earthen bridge, and a large, two-story inner gate containing a timber-framed gatehouse. Even if enemy forces successfully penetrated the outer gate and entered the courtyard, they were prevented from entering the castle grounds by the large internal gate. Ushigome-mon Gate’s design enabled forces defending the Castle to attack the enemy from the walkway in the gatehouse’s upper tier and positions atop the stone walls surrounding the courtyard. In 1872, the Ministry of the Army assumed control of Edo Castle and were tasked with protecting the Imperial Palace. After taking control, they announced that many of the existing gates would be torn down in the name of security. Ultimately, they order the removal of 21 of the outer gates. The Ministry of the Army then assumed responsibility for guarding and maintaining the gates that remained in place. In an effort to develop Tokyo’s urban infrastructure, the Tokyo prefectural government moved carried out the actual work of removing the castle gates, elevated walkways above the gates, stone walls that surrounded many of the gates, and the earthen fortifications in their vicinity. In 1902, after the elevated walkway above Ushigome-mon Gate had been removed a portion of the stone walls surrounding its inner sections were torn down. However, the eastern and western walls were left in place and remain in existence today. The original form of the square courtyard that surrounded the gate is indicated by the surface of the road constructed in its place. It enables visitors to grasp the layout of the square courtyard that surrounded the Gate’s inner portion. The exhibit on the first floor provides a detailed description of the stone walls’ struc-ture. A cornerstone retrieved from the side of one Ushigome-mon Gate’s stone wallsis emblazoned with two seals: those of Hachisuka lemasa and Hachisuka Tadahide, who supervised. the construction of Ushigome-mon Gate’s walled courtyard.
神楽坂（新宿区）側に残る橋台 The Remained Bridge Stage Beside Kagurazaka 1989（平成元）年の地下鉄南北線工事における発掘調査で、牛込橋の新宿区側の橋詰に高さ9.5mの牛込見附の土橋の石垣が確認されました。石垣は軟弱な地盤の下位にある強固な砂層地盤を支持層として梯子胴木を敷いた上に築かれており、弱い地盤施工する際の工夫が伺えます。その他、当時の土橋の側溝の構造がわかる遺構なども発見されています。
An archaeological excavation carried out in 1989 in conjunction with the construction of Tokyo’s Nanboku Subway Line uncovered a 9.5-meter-high stone wall from the Shinjuku Ward-side approach to Ushigome-mon Gate’s earthen bridge. The stone wall was constructed on top of a crib base, which served as a support layer for the hardened stratum of sand comprising the bottom tier of the site’s weak foundation. This discovery provides us with insight into the techniques used during the Edo period when building on sites with an unstable foundation.
牛込門・牛込駅周辺の変遷 The Transition of Usigome-mon Gate and Ushigome Station Areas 外堀は、1660（万治３）年、牛込・和泉橋間の堀さらいが行われ、外堀（神田川）をさかのぼって、牛込橋までの通船が可能となり、神田川沿いに河岸ができました。牛込橋東側の堀端には、揚場町の「町方揚場」と御三家のひとつである「尾張様物揚場」があり、山の手の武家地や町人地へ薪や炭などの荷物を運ぶ軽子が、「軽子坂」を往来したといわれています。 牛込門から城内に入ると武家屋敷が連なり、他方、堀端から現在の神楽坂の辺りは、善国寺（毘沙門天）の坂下の地域が武家地、早稲田側には寺町が形成されました。寺の門前には町屋が建ち並び、江戸名所の一つとして賑わいを見せていました。 明治になると、城外の新宿区側には、空き家と化した武家屋敷跡が芸妓置屋や料亭となり、神楽坂花街が形成されていきました。他方、城内の千代田区側の武家屋敷跡に学校などが建てられました。 牛込土橋東側の堀は、1984（昭和59）年、再開発事業により暗渠となり、現在に至っています。また、鉄道整備においても削られずに残された牛込門周辺の土塁は、1911（明治44）年、牛込・喰違間の土手遊歩道を外堀保存のため公園とする計画が決定され、1927（昭和２）年、「東京市立土手公園」として開設されました。現在でも国史跡指定区域に、外濠公園として歴史的風致が保全されています。
In 1660, the section of the outer moat located between Ushigome-bashi and Izumi Bridges was dredged. This made it possible for boats to travel up the outer moat (Kanda River) to Ushigome-bashi Bridge. In addition, banks were constructed on both sides of the Kanda River. The bankside area on the eastern side of Ushigome-mon Bridge was home to the Agebachō neighborhood’s “community landing,” and “the Owari House Landing,” which was controlled by the Owari, one of the three branches of the Tokugawa clan. Both sites were used to offload arriving cargo. Porters transporting firewood and charcoal to warrior estates and commoner neighborhoods in the Edo’s Yamanote area are said to have traveled from these moat-side landings up an incline known as Hill of Karuko. Entering the castle grounds from Ushigome-mon Gate, warrior estates lined the street. The area located at the foot of Zenkoku Temple between the moat banks and present-day Kagurazaka was home to warrior estates and, on the Waseda side, there were Buddhist temples. Commoner residences lined the space in front of the temple gates and the area emerged as one of Edo’s most bustling sites. Entering the Meiji period, unoccupied former warrior estates outside the castle walls on the Shinjuku Ward side came to host restaurants and establishments employing geisha entertainers and courtesans. This led to the establishment of the Kagurazaka pleasure quarter. In contrast, schools and other institutions were constructed on the grounds of abandoned warrior estates inside the castle wall on the Chiyoda Ward side. In 1984, the moat on the eastern side of Ushigome-bashi Bridge was enclosed in conjunction with a local reedevelopment project. It remains covered today. In addition, in 1911, the government presented a plan to transform the portions of the moat embankment in the vicinity of Ushigome-mon Gate that survived the construction of the railroads into a public park and preserve remaining portions of the outer moat between Ushigome and Kuichigai as a pedestrian walkway. This resulted in the creation of Tokyo Dote City Park, which was founded in 1927. Even today, historic landscapes located inside the area officially designated as a national heritage site have been preserved in the form of Sotobori Park.
甲武鉄道国有化・複々線化と飯田橋駅 The Nationalization of Kobu Railways and Construction of Multiple Lines and Iida Station 1906（明治39）年に甲武鉄道は国有化され、1909（明治42）年に中央東線（1911（明治44）年に中央本線に改称）の一部となりました。 甲武鉄道の乗客数は、開業した1894（明治27）年には85万８千人、翌年には242万２千人と急増していました。大幅に増えた旅客輸送に対応するため、汽車・貨物と電車の分離を目的に、1922（大正11）年から複々線化工事が行われました。複々線化の際、牛込駅下りホーム等が支障となったため、1928（昭和３）年に電車線の飯田町駅（現在の千代田区飯田橋三丁目）と統合する形で、そのちょうど中間となる曲線位置に飯田橋駅が開業しました。 開業当時の飯田橋駅は両端に出口があり、東口側は高架駅のような構造になっている一方、西口側は橋上の駅舎でした。この西口は旧牛込駅の利用者に対して影響が少なくなるよう設けられたものであり、長い通路が造られ、2016（平成28）年まで使用されていました。駅の屋根は古レールを使って作られ、現在もホーム上から確認することができます。 飯田橋駅のホームは急曲線にあったため、車両の大型化に伴いホームと電車の間には広い隙間ができていました。2020（令和２）年に、ホームを牛込駅があった市ヶ谷駅寄りの直線部分に移設し、より安全な直線ホームに改められました。あわせて、地域のシンボルとして史跡を活かした駅前広場や駅舎が整備されました。
JR 東日本中央本線【飯田橋駅】ホーム上屋古レール全景
冒頭でも触れた西口への通路も古レールが下部構造に大量に使用されている。まるで線路上から撮影したような写真であるが、あくまでもホーム上から撮影したものであり、ホームの曲がり具合が相当のものであることを実感できる。奥に見える下駄ばきの建物が西口の駅舎である。
JR 東日本中央本線【飯田橋駅】西口通路古レール全景
同通路を西口改札外の牛込橋付近より見下ろす。これだけの長さで立ち上がる古レールが延々と続くのは壮観である。しかし、現在の耐震基準ではまずアウトではなかろうかと思われる華奢な架構とも言える。一体どのような構造計算の結果で OK となったのだろうか。
JR 東日本中央本線【飯田橋駅】西口通路古レール全景
Kōbu Railway was nationalized in 1906 and became part of the Chūōtō Line in 1909. Two years later, the Chūōtō Line’s official name was changed to the Chūō Main Line. In 1894, Köbu Railway’s ridership numbered 858,000. By the following year, it had nearly tripled to 2,422,000. In 1922, additional lines were constructed in order to accommodate the line’s rapidly expanding ridership and to separate the steam and freight lines from the electric passenger lines. In 1928, Ushigome Station was merged with Iidamachi Station (present-day Chiyoda Ward Iidabashi 3-chome) because the platform for its outbound line obstructed the construction of the additional lines. This led to the creation of Iidabashi Station, which was located along a curve section of track equidistant from Ushigome and Iidamachi Stations. At the time of its opening, there were entrances at both ends of Iidabashi Station. While the eastern side had an elevated, viaduct-like structure, the eastern portion was located on a bridge. In order to accommodate passengers who previously boarded the train at Ushigome Station, a long passage connecting Iidabashi Station with its western entrance was constructed and remained in use until 2016. The Station’s roof was constructed using old pieces of rail track. These sections of the roof are visible today from the station platform. Because Iidabashi Station was located along a sharp curve, the construction of larger rail cars resulted in a wide gap between the platform and trains that served the station. In 2020, the platform was relocated to the straight section in the direction of Ichigaya Station previously occupied by Ushigome Station. This narrowed the gap between the platform and trains and made it safer for passengers to board. In conjunction with the platform’s relocation, a station-front plaza and station XX, was constructed.
Ushigome Station opened on October 9, 1894, the same day that Kōbu Railway initiated service between Shinjuku and Ushigome Stations. Before Iidama-chi Station opened on April 3, 1895, Ushigome Station served as the starting station on the Kōbu Line. Ushigome Station was located on the portion of present-day Iidbashi Station that extends from Ushigome Bridge in the direction of Ichigaya Station. At the time, portions of the outer moat were reclaimed in order to construct the station house and train tracks. Ushigome Station’s platform was located on the site currently occupied the JR Chuo Rapid Transit Line. In addition, the station house was constructed on the site currently occupied by the JR Chuo and Sobu Local Lines. Ushigome Station had two ticket gates. One was located on the present-day Shinjuku Ward side and the other was located on the Chiyoda Ward side. The gate building on the Chiyoda Ward side was constructed facing the road alongside the outer moat’s embankment and could be accessed by a staircase that rose from the Station’s rail bridge and climbed the embankment. A retaining wall from a section of the embankment next to the station house remains in place today in the vicinity of the entrance to Sotobori Park. On the Shinjuku Ward side, a road was constructed on land reclaimed from alongside Ushigome-mon Gate’s earthen bridge. Thereafter, Ushigome Station could be reached via a small pedestrian bridge, which was erected near the aqueduct attached to Ushigome-mon Gate’s weir. Today, portions of the foundation that supported the pedestrian bridge remain in place and are visible from Iidabashi Station’s platform and atop Ushigome Bridge.
These two maps indicate the location of historical sites in the vicinity of Iidabachi and Yotsuya Stations. The sites offer vital insights about Tokyo’s history from the early modern to the modern period. The map on the left traces the path of early modem Japan’s “Five Routes,” which radiated out in all directions from central Edo’s Nihon-bashi Bridge, and indicates the location of the city’s entrance gates and post stations on its periphery. The second map is a jurisdictional map indicating the territories under the authority of the Edo City Governor. It shows that areas inside the Yamanate Line comprised the city center and that the city area extended over a vast space that stretched far east as present-day Kinshicho Station.
喰違（The Remains of Kuichigai Gate）外堀で唯一土塁を組み合わさせた門で、1612（慶長17）年に完成しました。現在も原形を確認できます。
赤坂門跡（The Remains of Akasaa-mon Gate）江戸城外郭門で、1639（寛永16）年に完成しました。石垣は一部現存し、福岡黒田家の刻印がみられます。
飯田橋周辺案内図
牛込駅（千代田区側）駅舎跡
牛込駅（千代田区側）駅舎跡 甲武鉄道時代、ここには牛込駅の出入口がありました。 現在でも、当時作られた駅舎の左右にあった石積み擁壁がそのまま残されており、見ることができます。 The Remains of Ushigome Station 石積み擁壁 高低差のある土地で土砂崩れを防ぐために設置し、石を積んだ壁。
牛込門枡形石垣跡の舗装表示 かって牛込門の枡形石垣があった位置が自然石舗装で表現されており、その大きさを体感することができます。 Remnants of Ushigome-mon Gate’s Stone Walls 枡形 ますがた。石垣で箱形（方形）につくった城郭への出入口。敵の侵入を防ぐために工夫された門の形式で、城の一の門と二の門との間にある２重の門で囲まれた四角い広場で、奥に進むためには直角に曲がる必要がある。出陣の際、兵が集まる場所であり、また、侵入した敵軍の動きをさまたげる効果もある。
石に刻まれた印
石に刻まれた印 かつて牛込門の枡形石垣を構成していた石垣石が移設展示されています。 枡形石垣の整備を担当した徳島藩蜂須賀阿波守の刻印とみられるものが確認できます。 Inscriptions on the Stone
江戸城外堀跡散策案内図
江戸城外堀跡散策案内図
散策モデルルート Ａルート：「外堀散策ルート」Edo Castle’s Outer Moat
周囲14kmの江戸城外堀を史跡中心に巡ります。 This walk visits heritage sites along the outer moat’s 14-kilometer periphery Ｂルート：「江戸城内ルート」Edo Castle
牛込門から北の丸の田安門を経て旧江戸城本丸跡を巡ります。 Departing from Ushigome-mon Gate, this walk passes through the Northern Citadel’s Tayasu-mon Gate before visiting the remains of Edo Castle’s Inner Citadel. Ｃルート：「外堀水辺散策ルート」The Outer Moat Riverside Walk
神田川と日本橋川にある鉄道遺産などを巡ります。 This route visits sites along the Kanda and Nihonbashi Rivers relates to local railroad development.
The section of the outer moat located between Ushigome to Ichigaya was constructed by utilizing the topography of the Kanda River valley. In addition, because the Yotsuya and Kojimachi sections of the moat were located on a ridgeline, which cut across the Kanda Plateau, moat construction in those areas required the execution of a large-scale infrastructure project in which sections of the Plateau were removed and the moat was extended to the valley in the vicinity of the reservoir on the Akasaka side. Groups of domainal lords were mobilized to carry out the project and each group was required to remove a predetermined amount of earth from the plateau. The outer moat reached its highest point in the vicinity of Kuichigai Gate. From there, the water level gradually lowered as it passed through the channels linking Sanada-bori Moat with the Kanda River. In order to control the flow of water and prevent flooding, weirs were constructed to around gates, such as Ushigome-mon Gate, which were located on earthen bridges. These weirs were then utilized to control the water level in the moat. Furthermore, utilizing the natural topography, large earthen fortifications were constructed by building up sections of the Kanda Plateau on the present-day Chiyoda Ward side of the moat in order to improve the Castle’s defenses. That project resulted in the establishment of a steep embankment. Edo Castle’s outer moat boasts a total length of approximately 14 kilometers. The approximately 4-kilometer, 38-hectare section between Ushigome and Akasaka Gates is a designated as a National Historic Site. Visitors to the site can see the ingeniously constructed outer moat filled with water, the stone walls of the Castle’s outer gates, and the shape of its earthen fortifications.
江戸城 The History of Edo Castle 江戸城は、平安時代末の江戸氏居館、室町時代の太田道灌、戦国時代の小田原北条氏の支城として受け継がれました。豊臣秀吉は、北条氏を滅ぼすと、徳川家康を関東に移封しました。1590（天正18）年、徳川家康は江戸城に入城し、江戸城と城下町の建設を始めました。家康入城時の江戸城には石垣はなく土塁のみで、日比谷も入り江で日本橋・京橋辺りも海面と同じ高さの湿地でした。 家康は、まず城内の寺を出し本丸を拡張し、城下町の武家地、町人地を整えました。次に、本丸の南の台地を削り西の丸を造成し、その残土で日比谷入り江を埋め立てました。1603（慶長８）年、幕府を開き実権を握った家康は、天下普請として、城と城下町建設に諸大名を動員しました。同じ年に、神田山を崩して日本橋南の地域を埋め立て、市街地の造成と日本橋の架橋を行い、翌年には日本橋を起点とする五街道を整備しました。1606（慶長11）年には二の丸・三の丸と城郭の整備、石垣築造を進め、翌年には天守が完成しました。なお、天守は1657（明暦３）年に大火で焼失した後、再建されませんでした。 1868（明治元）年、明治天皇が江戸城に入り皇居となり、1960（昭和35）年、江戸城内郭の堀が「江戸城跡」として国の特別史跡に指定されました。このほか、「江戸城外堀跡」と「常盤橋門跡」が史跡に、外桜田門、田安門、清水門とそれぞれの櫓門が重要文化財に指定されています。
Edo Castle’s origins can be traced to the establishment of the Edo Clan’s estate in the late-Heian period. During the Muromachi period, it served as the location of Ōta Dōkan’s branch castle. Entering the Warring States Period, it was controlled by the Hōjō Clan’s and served as the site of their branch castle. When Toyotomi Hideyoshi eradicated the Hōjō Clan in the late-sixteenth century, Tokugawa Ieyasu was sent to their former territory in the Kantō region. In 1590, leyasu assumed control of Edo Castle and initiated the Castle’s reconstruction and construction of the surrounding castle town. At the time, there were no stone walls on the Castle site. The only remaining features of the Hōjō Clan’s branch castle were its earthen fortifications. In addition, the Hibiya area was an inlet and the Nihonbashi and Kyōbashi areas were low-lying wetlands. leyasu began the reconstruction effort by removing temples from the site, expanding the Castle’s inner citadel, and supervising the construction of the city’s commoner districts and warrior estates. He then removed portions of the plateau immediately south of the inner citadel and constructed the western citadel. In addition, the inlet in Hibiya was filled in using the earth removed from the plateau. In 1603, leyasu, who had by then seized national political authority and established a tent government, mobilized domainal lords from the across the country to construct the remaining portions of Edo Castle and the surrounding city area. The same year, Kanda Hill was leveled and earth removed from the Hill was used to fill in the southern portions of the Nihonbashi area. The area was then developed and Nihon-bashi Bridge was constructed. The following year, an archipelago-wide network of five overland circuits originating from Nihon-bashi Bridge was established. In 1606, the second and third citadels and castle tower were constructed and work continued on the stone walls surrounding the Castle. By the following year, the Castle’s main keep was complete. In 1657, however, the Castle was destroyed by a fire and had to be reconstructed. In 1868, the Meiji emperor moved to Edo Castle and it came to serve as the imperial palace. In 1960, Edo Castle’s inner moat was classified as Edo Castle’s official ruins and designated a National Heritage Site. In addition, remaining portions of the Castle’s outer moat and the ruins of Tokiwabashi Gate received designation as Historical Landmarks. Lastly, the box-shaped, two-story gatehouses at Sakurada-mon, Tayasu-mon, and Shimizu-mon Gates were designated as Important National Treasures.
