10 Best Adventures in Maui: Hikes, Snorkeling & More | Condé Nast Traveler

"Back in the days when this region was volcanically active, lava flowing into the ocean would cool on the outside, then drain out on the inside—resulting in long, cylindrical "tubes." Today, as you're driving along Maui's famous Road to Hana, you can channel your inner Indiana Jones—or perhaps Elsa Schneider—and descend a few flights of stairs to see this geological phenomenon for yourself. Educational signs throughout the cave point to the highlights of the lava formations, including contraction cracks, stalagmites and stalactites, puzzle pieces, overflows, and more." - Todd Plummer