Through Pond, located on Shimoji Island in Miyakojima City, is a mysterious place where two circular ponds, one large and one small, are connected underground. The first pond is 75 meters in diameter and 45 meters deep. The second pond is 55 meters in diameter and 25 meters deep. From the ground, the two ponds appear to be side by side, but they are connected underground, and the pond on the ocean side is connected to the ocean through a cave. The pond on the ocean side is connected to the sea by a cave.
Because the pond is connected to the ocean, the surface of the water rises and falls with the ebb and flow of the tide. The salinity and temperature of the water varies depending on its depth, making it a habitat for a variety of fish and shellfish. It is also a popular diving spot.
The formation of the Through Ponds began when stalactite caves on the coast were eroded by waves and grew in size. The ceiling partially collapsed to form a sunken doline, which allowed seawater to enter and create Through Pond. Surrounding the site is a karst landscape known as the Karenfeldt, which is home to a variety of academically valuable plants. In recognition of this natural environment, the area was designated as a national scenic spot and natural monument in 2006.
Beyond the Through Pond, similar sunken dolines are scattered around, and one of them, Nabeshi Pond, is also connected to the sea by a cave. A boardwalk was maintained, but was damaged by a typhoon in 2016 and is now closed to traffic.
Free of charge
20 minutes drive from Sarahama Port