Also known as Jiugong Tunnel (九宮坑道), this four-entrance network of wide sea tunnels was blasted out of the gneiss in the 1960s to provide bomb shelters for as many as 50 small boats.
A few mannequins show the labour-intensive drilling processes, while a water-free former hospital section contains a visitor centre with exhibits on Little Kinmen's geology and other attractions. To find it from the ferry dock, simply walk left along the promenade. There are alternative tunnel access points near the bike-hire sheds and from Luocuo fishing village.
