, also known as the , is a forest on the northwestern flank of Japan's Mount Fuji, thriving on of hardened lava laid down by the last major eruption of Mount Fuji in 864 CE. The western edge of Aokigahara, where there are several caves that fill with ice in winter, is a popular destination for tourists and school trips. Parts of Aokigahara are very dense, and the porous lava absorbs sound, helping to provide visitors with a sense of solitude.