Kumejima, Japan

Located 90 km (56 miles) to the south-west of Okinawa Honto, Kumejima is a multifaceted island home to natural treasures. Hatenohama, a stunning 7 km-long (4.3 miles) fine-sand beach, promises wonderful carefree moments discovering the exceptional underwater worlds off the coast of Kumejima. Mifuga, a rock formation on the north coast of the island with a hole right through its middle, is a great example of the erosion along the coast. The eastern peninsula offers another geological feature, visible at low tide: 1,000 flat rocks each around one metre (3.2 feet) in diameter, formed by the contraction of lava from a nearby eruption a million years ago. They create a rocky plateau resembling a traditional Japanese tatami, hence the name Tatami-ishi.