It is located northwest of Asukadera Temple and the eastern part of the Asukagawa River. Mizuochi Ruins are located in the northwest corner of Asukadera Temple, and Ishigami Ruins are located further north.
Mizuochi Ruins have the unique structure of 7th century construction, which is called Houkei Kidan. Houkei Kidan is a type of podium with an ancient square with corner stones.
The podium (a square 22.5 meters on each side and 1 meter in height) got the square shape by piling up 3 to 4 natural stones. It has moats of 1.8 meters in depth around.
There was a pavillion with Houshiken Soubashira (11 meters pillar per each) on top of its podium.
The "Ma Ma" stone is located in the centre of the podium. By linking with other cornerstones, it gives us the impression of its dignity.
A wooden box coated with lacquer is located in the centre of its podium. In this wooden box, Mokuhi Ankyo (waterworks with wooden pipes) and bronze pipes with siphon style were created to pump water from the Yatsurigawa River to work as a water clock.