Puna
The 2018 Kilauea eruption buried 35 square kilometers of the Puna District under 20–30 meters of lava — entire neighborhoods, the former Kaimū Black Sand Beach, and the historic Royal Gardens subdivision. Walking through Kalapana's lava fields today is like walking on the surface of a different planet: standing dead palm trees emerging from black lava, the outline of buried roads and mailboxes still visible, new black sand beach forming where the 2018 lava met the ocean. Kehena Black Sand Beach, 10 minutes along the coastal road, is an exhilarating and raw destination: clothing-optional by local custom, accessed by a steep cliff trail, with spinner dolphins frequently in the bay and strong body-surfing waves. Go for the Puna coastal road (Hwy 137) even if you skip the specific stops — the jungle-lava-sea combination is unlike anywhere else.
Free, no reservation. Drive to Kalapana on Hwy 130, ~45 min from Hilo. The road through the Puna District (Hwy 137 coastal road) is one of the most scenic on the island. Kehena Beach is accessed via a steep, unmarked trail — park on the roadside on Hwy 137 and look for the path.
Year-round. Kehena beach can have strong shore break — assess before entering. The coastal road may be partly closed after new eruptions; check HDOT before driving.