Tongyeong Undersea Tunnel, Undersea tunnel in Tongyeong, South Korea.
The Tongyeong Undersea Tunnel is a pedestrian passage in Tongyeong, South Korea, running beneath the sea to connect the city's mainland side with Mireukdo island. The concrete structure is about 5 meters wide and sits roughly 13.5 meters below sea level at high tide, spanning a total length of around 483 meters.
The tunnel was built in 1932 during the period of Japanese administration and was the first undersea tunnel on the Asian continent at the time of its construction. It is now listed as a Registered Cultural Property of the Republic of Korea.
At the entrance of the tunnel, a Chinese inscription reads 'Yongmundaryang', which translates roughly as 'the gate of the dragon'. This name draws on an old local belief that a dragon guards the sea passage between the mainland and the island.
The tunnel is open to pedestrians and can be walked without any special equipment or preparation. It is worth checking local conditions and opening times before visiting, as access may vary depending on the tides.
The tunnel was designed with a ventilation system built specifically for underwater use, and parts of this original system are still in place today. Most visitors walk through without noticing it, yet it is one of the clearest signs of how carefully the structure was planned for its time.
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