Near the start of Mauna Loa Rd, there's a turnoff to some neglected lava tree molds – deep wells that formed when lava flows engulfed the rainforest and hardened around the waterlogged trees instead of burning them upon contact. As the trees disintegrated, they left holes where the trunks once stood. Some are now sprouting new trees, but most are collecting trash.
Lava Tree Molds
Hawaiʻi Volcanoes National Park