The Kanohina Lava Tube system is about 1,000 years old and was used by the ancient Hawaiians for water collection and for shelter. More than 40 miles of these braided lava tubes have been mapped so far in the Kau District of the Big Island, near South Point. About 45 miles south of Kailua-Kona, these lava tubes are a great experience for cavers of all age levels and abilities.

Kula Kai Caverns. Expert cave guides lead groups into the fantastic underworld of these caverns near South Point. The braided lava-tube system attracts scientists from around the world, who come to study and map them (more than 40 miles so far). Tours range from the "Lighted Trail" (in the lighted show cave, which is easy walking), to the "Two Hour," a deep-down-under spelunking adventure that often takes closer to three hours and allows you to see archaeological evidence of the ancient Hawaiians. Longer, customized tours are also available and programs are tailored to each group's interest and abilities; all gear is provided. Tours start at an Indiana Jones–style expedition tent, complete with a topographic map and divulge fascinating details about the caves' geologic and cultural history. Reservations are required. Kula Kai Estates, Lauhala Dr. at Kona Kai Blvd., Hawaii, 96737. 808/929–9725; From $20.