Heian-kyo

It was an ancient Japanese imperial capital dating back to 794 (Enryaku 13). It was located in an area (present-day Kyoto City) that straddled the Atago and Kadono counties of Yamashiro Province (Yamashiro Province), and continued to exist until 1869 (Meiji 2), when the capital was transferred to Tokyo. The northern Yamashiro region, where Heian-kyo was established, was notable for two reasons. The first was its advanced nature as a region. The Katsuragawa, Kamogawa (Kamogawa), Ujigawa, and Kizugawa rivers, as well as the Yodogawa river, which merged with the Katsuragawa, were flowing through the area, and water transportation was extremely well developed. The same was true for land transportation, with the Hokuriku road, known as the Yamashiro road, and the San'in road, known as the Tamba road, passing through the area. Easy transportation is an essential condition for an ancient imperial capital, and this ease of land and sea transportation was one of the reasons for the construction of Heian-kyo. The second reason is the tradition of the imperial capital. As Heian-kyo continued to be the imperial capital into modern times, when people think of Yamashiro Province and Kyoto, they often only think of Heian-kyo, but there were four imperial capitals that preceded Heian-kyo: Tsutsuki-no-miya and Otokuni-no-miya of Emperor Keitai, and Kuni-kyo of Emperor Shomu, not to mention Nagaoka-kyo, which came just before it. It was on this tradition that Heian-kyo was built. Furthermore, while the construction of Nagaoka-kyo was carried out under extremely unstable political circumstances, including the assassination of Fujiwara no Tanetsugu the year after the capital was moved, in the case of Heian-kyo, a land survey was conducted in January 793 and things proceeded smoothly until the capital was moved in October of the following year.

The plan was modeled on the Tang Dynasty's imperial capital Chang'an, with unique Japanese features added. It is similar to Chang'an in that it has a central axis (bilateral symmetry), is oriented north-south, and the palace and capital areas are separate, but there are many differences, such as its longer north-south length and its size being less than one-third that of Chang'an. Heian-kyo covered 4.5 kilometers (1508 jo) from east to west and 5.3 kilometers (1753 jo) from north to south. The palace area (Daidai-ri) was located toward the north center, and the capital area spread out to the east, west, and south of that. In the center was the 84-meter-wide (28 jo) Suzaku-oji Avenue, which connected Rajomon, the main gate of Heian-kyo, with Suzakumon, the entrance to the palace area. It seems that there was a castle wall on the south side, which imitated the walled castle that surrounded Chang'an Castle, but in Heian-kyo it was only built on the south side. This is because Japan did not have the military situation of being constantly exposed to invasions by foreign tribes like Chang'an. Ichijo-oji was the northern limit, and there were 11 main roads between Kujo-oji at the southern limit, and nine main roads between Higashi-kyogoku-oji at the eastern limit and Nishi-kyogoku-oji at the western limit. These 20 main roads were the main roads of Heian-kyo, and countless small roads were laid out in all directions based on these. The capital was administered by the left and right Kyoto officials, and was a special district different from the general administrative districts such as Kinai and Shichido. The interior was divided into jo, bo, ho, and cho, and the smallest unit was the head of a household, which was 10 jo deep and 5 jo wide, or 30 meters by 15 meters. As the name of the head of the household indicates, this was established as the residence of a standard single family, indicating that Heian-kyo consisted only of residential land, meaning that it was an area with no farmland.

Heian-kyo underwent changes in the mid-Heian period. Ukyo, which was dry and humid near the Katsura River, fell into decline, while only Sakyo developed. Furthermore, new urban areas expanded beyond Ichijo-oji to Kitano, and beyond Tokyo-gyoku-oji to the area around the Kamo River. The planned standards of Ichijo, Kujo, Tokyo-gyoku, and Nishikyogoku began to collapse. Heian-kyo continued to be the imperial capital in the following periods, but this was the end of Heian-kyo as a political city.

[Inoue Mitsuro]

“Research History of Heiankyo” written by Mitsuro Inoue (1978, Yoshikawa Kobunkan)

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

794年（延暦13）から始まる日本の古代宮都。山背国(やましろのくに)（山城国）愛宕(おたぎ)・葛野(かどの)両郡にまたがる地（現京都市）に置かれ、形式的には1869年（明治2）の東京奠都(てんと)まで続いた。平安京の営まれる北部山背は、二つの点において注目される地域であった。第一は、地域としての先進性である。桂川(かつらがわ)、賀茂川(かもがわ)（鴨川）、宇治川(うじがわ)、木津川(きづがわ)や、さらにそれらが合流した淀川(よどがわ)が流れており、水上交通の著しく発達した地域であった。陸上交通も同様で、山背道とよばれた北陸道、丹波(たんば)道と称された山陰道が通過していた。交通の利便は、古代宮都の備えるべき必須(ひっす)条件であるから、このような水陸交通の便のよさは平安京造営の原因の一つとなった。第二は、宮都の伝統である。平安京は結果として近代まで宮都であり続けるから、山城国・京都といえば平安京しか思い浮かばないことが多いが、その直前の長岡京はいうまでもなく、それ以前にも継体天皇(けいたいてんのう)の筒城宮(つつきのみや)・弟国宮(おとくにのみや)、聖武天皇(しょうむてんのう)の恭仁京(くにきょう)と、平安京に先行する4宮都をもっていた。この伝統のうえにたっての、平安京造営であった。なお、長岡京が、遷都の翌年に藤原種継(ふじわらのたねつぐ)暗殺事件を起こすなど、きわめて不安定な政治状況下で造営が進められたのに対して、平安京の場合は、793年1月に土地調査が行われ、翌年10月に遷都するまで事態はスムーズに運んでいる。

　平面形態は、唐(とう)の宮都長安をモデルとして、これに日本独自の特色が加味されて設計された。中軸線をもつこと（左右対称型）、南北方向であること、宮域と京域が分離されていることなどは長安に類似するが、南北が長いこと、大きさは3分の1以下にすぎないことなど相違する点も多い。平安京は東西4.5キロメートル（1508丈）、南北5.3キロメートル（1753丈）を占めた。中央北寄りには宮域（大内裏(だいだいり)）が位置し、その東・西・南面に京域が広がっていた。中央には幅84メートル（28丈）の朱雀大路(すざくおおじ)があって、平安京の正門ともいうべき羅城門(らじょうもん)と宮域の入口の朱雀門とを結んでいた。南面には城壁があったようで、これは長安城の四周を巡る羅城を模倣したものであるが、平安京には南側だけにしか築かれなかった。長安のように絶えず異民族の侵入にさらされるという軍事的状況が日本にはなかったからである。一条大路を北限とし、南限の九条大路間に11本の大路、東京極大路(ひがしきょうごくおおじ)を東限として西限の西京極大路間に9本の大路、この合計20本の大路が平安京の主要道路であり、これを基準として無数の小道が縦横に敷かれた。京域は左右の京職(きょうしき)が管轄し、畿内(きない)・七道といった一般行政区画とは異なった特別区とされた。内部は条・坊・保・町に区分され、最小の単位は戸主(へぬし)で、奥行10丈・幅5丈、すなわち30メートル×15メートルであった。戸主の文字が示すように、標準的な一戸の家族の居住地として設定されたものであって、平安京が宅地のみからなるものであったこと、つまり農地をもたない地域であったことを示している。

　平安時代中期に至り、平安京は変化する。桂川に近く低湿であった右京が衰退し、左京のみが発達するようになった。さらに一条大路を越えて北野、東京極大路を越えて鴨川周辺へと、新たに市街が展開した。計画された一条・九条・東京極・西京極という規格が崩壊し始めたのである。宮都であるという点ではこれ以後の時代も同様であるが、政治都市としての平安京はここで終わったといえる。

［井上満郎］

『井上満郎著『研究史平安京』（1978・吉川弘文館）』

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