On Kilauea's eastern side, Crater Rim Dr passes through rainforest kipuka (oases) thick with tree ferns and ohia trees. An often overflowing parking lot is the access point for the ever-popular Thurston Lava Tube. All the tour buses stop here and it's a favorite with kids, so plan to come early or late in the day. A 0.3-mile loop walk starts in ohia forest filled with birdsong before heading underground through a gigantic lava tube that's artificially lit.
Lava tubes are formed when the outer crust of a lava river starts to harden but the liquid lava beneath the surface continues to flow through. After the flow drains out, the hard shell remains.
