Tatsuoka Castle, a pentagon-shaped castle
Saku's most popular destination is Tatsuoka Castle Ruins. Tatsuoka Castle is known as one of the two western-styled, pentagon-shaped castles built in the 1860s to fight against western powers. Another of the Goryokaku in Hakodate much larger western-styled castle is so popular, this one had been left forgotten until recently. Much of the castle ruins is now a part of an elementary school. But unlike Tanaka Castle in Fujieda they made great effort to keep Kitchen Building the only castle building left and most of the water moat.