Shiryokaku Fort is Goryokaku’s lesser-known little brother. It sits on a gentle slope about three kilometers (1.9 miles) northeast of Goryokaku, and was intended to protect that fort’s rear against attack.
“Shiryokaku” literally means “four-sided fortification” (“Goryokaku” means “five-sided fortification”). It's a very simple affair composed of earthen walls with four bastions surrounded by a dry moat. There's a shielded entrance on the south side, but there don’t seem to have been any permanent structures within the walls. Just as Goryokaku is often compared to a star, the shape of Shiryokaku is sometimes compared to a butterfly.
In April 1869, Shiryokaku was built in just two weeks under the direction of Otori Keisuke, commander-in-chief of the army of the Ezo Republic and his French second-in-command, Jules Brunet. So it was something of a Franco-Japanese co-production. However, imperial forces overran the fort in just a few hours on May 11 as the defenders retreated for their last stand at Goryokaku.
The photo above is the view from the northeast bastion with a clear view of the trench. The tower in the distance marks the site of Goryokaku. Mount Hakodate is behind that to the right.
Shiryokaku is worth a visit for hardcore castle fans and history buffs. Others might prefer to pass on it, although in the summer it's a great place for kids to catch bugs or for a game of frisbee.
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