The Beihai Tunnel is located between Renai Village and Meishi Village on the Matsu Islands. It was once a tunnel pier dug by the Taiwanese military in 1968 for the strategic needs of sheltering from wind and waves and shelling from the other side. It has now become a tourist attraction. The very well-known landscape in the tunnel is the reflection of the rock wall in the water. After being projected on the calm and waveless water, another tunnel is formed, which deepens the illusion of the height of the tunnel. It is quite spectacular; there are many gunpowders shot by air compressors on the rock wall. The hole shows the difficulty of digging at that time. Visitors can walk along the rock wall with a length of about 700 meters, and it takes about 30 minutes to make a detour.