Japan's first Western-style fort was built in 1864 in the shape of a five-pointed star (goryō-kaku means 'five-sided fort') designed to trap attackers in deadly crossfire. Nothing remains of the actual structure but the footprint – a park encircled by a star-shaped moat. To best appreciate this, visit the observatory atop the 98m Goryō-kaku Tower. Exhibitions in the observatory explain the history of the fort; you also get good views over Hakodate.

The park itself is a pretty green space, with 1600 cherry trees that bloom in April.