Aokigahara, also known as the sea of trees, is a forest on the flanks of Mount Fuji on the island of Honshu in Japan, spread over 30 square kilometres of rock hard lava which was laid down during the last major eruption of Mount Fuji in 864. The western edge of Aokigahara, where there are various caves that fill with ice in winter, is a popular destination for tourists. Parts of Aokigahara are very dense, and the porous lava rock absorbs sound, all adding to a sense of solitude that some visitors decide to be the perfect place to implement their final act.