King's Highway AKA Hoapili Trail

This trail traverses the last lava flow on Maui, in 1790. The trail has been used for hundreds of years - imagine Hawaiians hiking barefoot along these razor-sharp, ankle-rolling lava cobbles! The trail was rebuilt in 1824-1840, which makes even the "new" version pretty historic. The trail itself is miserable - straight across black, hot rock, far from the sea (hot!) and the surface is baseball-sizes lava rocks that seem to move with every step. But the destinations are pretty amazing: especially the turnoff to Keawanaku Beach, which has some of the finest swimming and snorkeling on the entire island, and you are very likely to have it to yourself. You can continue on for many miles, but the surface is rough-going and once you past the end marked here, you've seen the high points. Definitely not recommended to continue.