Type: Flatland
Built in: 1867 by Matsudaira Norikata
Class: Ruins

Tatsuoka Castle is one of the flatland castle located in Saku, Nagano Prefecture. It was constructed at the end of Edo period. It is very unique because the structure takes a shape of pentagon. So, it is the western style castle built in Samurai Era.

The last lord of this domain, Norikata loved the western style structure. He studied Dutch. Therefore, when he decided to built his castle, he designed it similar to Hakodate Goryokaku Castle in 1864.

Pentagon Structures and moat are preserved in a great condition. Each corner has strong stone structures that is called Kikko Layer that means tortoiseshell. It is very strong structure because each corner was designed for the large cannon.

Midaidokoro
Only remaining building. Constructed in 1875.