Abukuma-do is a limestone cave located in Fukushima Prefecture, Japan. The cave was discovered on August 15, 1969, northeast of the city of Tamura and was originally named Kamayama Shonyu-do. It was designated a natural heritage of the town on February 7, 1971 and renamed Abukuma-do on June 1, 1973. Visitors can traverse a 600-meter-long path inside the cave as well as a 120-meter-long exploration course to view the stalactites and stalagmites. Each stalactite has taken more than eighty million years to form. Beyond the public areas lie about 2,500 meters of cave that are not open to the public. Nearby Abukuma Cave is the smaller Irimizu Shonyu-do, discovered in 1927. Irimizu Limestone Cave was designated a National Natural Treasure on December 28, 1934. The temperature inside Abukuma-do is around 15°C and the humidity is above 90%.

Boxwork

A notable feature of Abukuma-do is the existence of boxwork, a rare cave formation composed of thin blades of the mineral calcite that project from cave walls and ceilings, forming a honeycomb or box-like pattern. Boxwork can also be found in Shimukugama in Okinawa and Sugawatari-do ( Ice Cross Cave) in Iwate Prefecture, but because Abukuma-do is currently the only limestone cave in Japan open to tourists, it is subsequently the only cave in Japan in which you can see boxwork.

Christmas Tree and Silver Frost

The Christmas Tree and the Silver Frost are two of the most distinctive Speleothem inside Abukuma-do. The Christmas Tree is a stalagmite and The Silver Frost meets dripstones on the roof of the cave resulting in an impressive column. Both represent a featured stop along the 600 meter course inside the cave. According to the Abukuma Caves Management Office, The Christmas Tree, at over two meters high, is said to be the largest stalagmite in the East.

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