石垣島 (Ishigaki Island) is a small island at the southern end of the Japanese island chain, 230 km east of Taiwan. It is the second-largest island of the Yaeyama Island group, behind Iriomote Island. It belongs to Okinawa Prefecture. The southern location makes this the sub tropical part of the country, and it is very popular with domestic tourism. There are tropical fruits and animals, most of the island and the surrounding waters, including Mount Omoto and Kabira Bay, are protected as part of the Iriomote-Ishigaki National Park.
The island is of volcanic origin, the central mountain, 於茂登岳 (Mount Omoto, 525 m asl) is the eroded remains of a granite intrusion from the Neogene Period. While granite does not contain any caves, the mountain is surrounded by coastal plain which consists of coral reef limestone. The plain is only 20 m to 50 m above sea level but at the southern coast it is up to 8 km wide. The limestone is karstified and contains numerous caves. The first cave which was opened to the public was named after the Island. It seems it was so popular, by now two more caves were opened as show caves, and one is in the making.
The coast is formed by limestone cliffs and has numerous small sea caves. One of them at the northern coast is called Blue Cave because the water has a great blueish tint. We did not list it as a blue cave, because it is actually not what we call blue caves on showcaves.com. It is only an overhanging cliff face, not a real cave.