Yakushima is my favorite world heritage site in Japan, hands down.
When I visited, I was the only non-Japanese person I saw on the island. Being located south of Kagoshima, the southernmost city on Japan's four main islands, it isn't on the radar for most tourists visiting Japan.
Yakushima was the inspiration for the animated film Princess Mononoke.
A cedar forest located in the clouds on top of the island, the mood can be very eerie and surreal.