Type : Mountain castle
Built in: 1221 by Toyama Kagetomo
Class: Ruins

Structure: Honmaru, Ninomaru, Sannomaru, and Demaru. No Tenshukaku, but two 2 stories keeps, and at Otemon gate which located in Sannomaru had a 3 stories keep which sometimes considered as the Tenshukaku.

Stone walls and baileys are well preserved especially Stone walls of Honmaru, the main bailey, is like another mountain on the top of mountain.

There are 11 keeps which surrounded Honmaru and all of them are directory controlled by Honmaru.

History
Iwayama Castle was built in 1221 by Toyama Kagetomo, but is was located on the ground level at that time.

In mid-16th century, Toyama and Takeda clan moved this castle to current location and built it much stronger castle.

In 1570, Takeda Shingen attacked this castle, but by the help of Oda Nobunaga, Iwamura Castle won against Takeda army.

In 1571, Toyama Kagetou died and Toyama clan was breached. To protect Toyama clan, Nobunaga's 5th son was adapted to Toyama clan. The wife of Kageto, Otsuya was also aunt of Nobunaga. Because new lord was only five years old, she support him and basically ruled the castle and area of Iwamura. Therefore, this castle was called the castle of woman lord.

In 1572, Takeda Shingen moved major part of his army to attack Tokugawa Ieyasu of Enshu. Iwamura was also attacked by Akiyama Nobutomo, samurai of Shingen. However, because this castle was strong, he couldn't defeated easily. Akiyama negotiated Otsuya and instead of giving this castle to Takeda, she agreed to married Akiyama and help other hostages. Nobunaga considered this as serious betraying of Oda clan.

In 1575, after the battle of Nagashino, Takeda Clan lost their power, and Nobunaga ordered to his son Nobutada to defeat this castle. Five month later, this castle was fallen and Nobunaga killed Otsuya and all other Toyama clan.

After, that Nobunaga gave this castle to Mori clan to protect Mino. Mori Ranmaru was once the lord of this castle. Nobunaga visited and stayed 80 days before he was killed in Honnoji.

After the battle of Sekigahara in 1600, Matsudaira Ienori became the lord of this castle and he built castle town.