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be determined from the roadside currently located parallel to the embankment, the original earth-reinforced walls have been replaced by small-scale concrete retaining walls.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.
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.
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.
