A Japanese Buddhist, Kuukai known as KoubouTaishi donated a wooden carving Kannon Bosatsu sculpture to Iwamuro Mountain in Heian period.

Successive loads of Musashi-Matsuyama supported this Iwadono Kannon Hall for many years.

In 1590, at time of attacking Musashi-Matsuyama castle by Maeda Toshiie, a supreme commander of Toyotomi side, the castle and Iwamuro Kannon Hall fell to the army. 

The present Kannon Hall was rebuilt in early Edo period by Gyoin Ⅲ of Ryusein temple.

This Kannon Hall was constructed by Kake-zukuri sane as Kiyomizu Temple in Kyoto. Its building method was constructed on a slope or cliff, and part of its floor was supported by a long pole. 

The Kannon Hall is said as Karamete gate (a rear gate of a castle) and there was the famous Tanka poem match.

In detail, refer to Musashi-Matsuyama.(E&OE)