National Tangible Cultural Property
The Ishizaki Fishing Port Tunnel was designed by Renji Nakamura, Director of the Port and Harbor Division of the Hokkaido Government.

The tunnel was hollowed out at the bottom of the cape, which is said to be the site of Hiishikan. It is 45 m long and 9 m wide, constructed of concrete blocks with a semicircular cross section, and was completed on June 20, 1934. At the time, it was the only one of its kind in the East and one of the few of its kind in the world.
The large protruding cape blocked the winds from the northwest to southwest, and fishing boats from neighboring harbors sometimes took refuge there during times of heavy seas. At the entrance on the open sea side, there was an iron tower with a 1.4-meter-diameter windmill, which rang a bell when the wind blew and turned.
The Ishizaki River beside the harbor flooded and large waves overtopped the breakwater, causing earth and sand to flow into the harbor and bury it, but each time this happened, the villagers worked together to restore and repair the tunnel.
Around 1967, as fishing boats became larger and larger, work began to expand the harbor, and a waterway was constructed on the north side of the tunnel.
In February 2006, it was recognized as one of the "100 Historical and Cultural Properties of Fishing Villages to be Preserved for the Future.