Fort Goryokaku is a massive European style star fort. It features low thick walls that protect it from cannon fire and a wide moat that protects it from climbing (infantry). It's star shape is designed to reduced the number of blind spots for the fort's cannons.
Today Fort Goryokaku is a park that's open to the public. It's the best spot in Hakodate for hanami (cherry blossom viewing). The park is also picturesque in autumn colors.
There's a 107 meter (350 foot) high viewing tower in front of the park that offers spectacular views of the fort.
At the center of the fort is a (reconstructed) Magistrate Office. This was the Shogun's war room — from which he planned his last stand against the Emperor.