Fuji Wind Cave first appears to be a big hole in the ground. It's a lava tube. You need a permit to enter. That's why having a licensed guide is good.

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Filename:	ya416-20191112_2243.jpg
Album name:	philbert / Aokigahara Forest and Lava Tube 青木ヶ原樹海・風穴
Keywords:	yamanashi / fujikawaguchiko / aokigahara / forest
Filesize:	59 KiB
Date added:	Jan 06, 2020
Dimensions:	600 x 400 pixels
Displayed:	22 times
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