You will find the Okunoin (Inner House) after you passed through the Koukamon Gate and went stone upstairs. There will be Copper Treasure Warehouse on the left of the Okunoin.

However, Koukamon Gate never opens to anyone because the Okunoin is located inside the gate. Even priests can rarely enter.

The Okunoin is the tomb of the third successive Shogun Iemitsu, and is the most majestic area in Taiyuin Mausoleum.

The Okunoin consists of Haiden oratory, Inukimon Gate and Hoto Treasure Tower. Frontage of the Okunoin Haiden is 9m wide, 5.4m deep, and fundamental color is black. Frontage of the Inukimon Gate is 2m, 1.5m deep. It is copper-molded, and Sanskrit carving is decorated.

Round pillars surround the Treasure Tower. It is copper-made and 4m high. Image of Shaka Nyorai and memorial tablet are put inside the tower. Dead body of Iemitsu has been enshrined under the tower calmly.