As mentioned in a previous entry, the heart of Heian Japan was the capital, Heian-kyō (modern day Kyoto). Though there's some debate about the reasons for the move, most scholars think that the key motivation was a desire to diminish the political influence of Buddhist temples located near the old capital and the influence of regional aristocrats antagonistic to the then imperial regime.
The city was created on the order of the Emperor Kammu. This was not a situation where an existing city or set of villages was adapted. This city was built up in a very deliberate, planned manner in conscious imitation of the Chinese Tang Dynasty capital. Geomancy and other related techniques influenced the design. Although we now view such techniques as supernatural, at the time they were treated with the respect we'd grant skilled engineers and architects.
Due to such considerations, the selected site had nearby mountains and flanking rivers. Although one can see the practical transportation value of rivers or the defensive values of mountains, these natural features were also believed to help contain evil influences.
The careful design of the city allowed for easy navigation. The overall borders of the city formed a rectangle (about 5.5 km north-south/4.7 km east-west). The Imperial palace complex was not centered in the city, but instead in the north center. It lay at the end of the city's main road, Suzaku Avenue. This road was extremely wide, about 85 m/280 feet). So, you can easily imagine the dramatic impact of walking down this huge road and seeing the palace grounds looming in the distance:
|A model reconstruction|
At the lowest level, jo (a little over three meters) made up square cho (the rough Heian equivalent of a city block). These cho were about 120 meters on each side (about 400 feet). The cho were further organized into groups of four with one group arrayed east to west and another north to south (jo* and bo, respectively). These were also numbered. In the end, given the square units involved, this allowed for an addressing system that was close to a coordinate system for major locations.
*Without getting bogged down in Japanese writing, the kanji (Chinese character) for this jo is different than the more basic jo.