2 Best Sights in Kau, Big Island

A must-do on a south-southeast-bound trip to the volcano, this easily accessible black-sand beach is backed by low dunes, brackish ponds, and tall coco palms. The shoreline is jagged, reefed, and rocky. Most days, large groups of sea turtles nap on the sand—a stunning sight. Resist the urge to get too close or disturb them; they're protected by federal and state law, and fines for harassment can be hefty. Removing black sand is also prohibited.  Extremely strong rip currents prevail, so only experienced ocean swimmers should consider getting in the water here. A popular stop for locals and tour buses alike, this beach park can get busy; the north parking lot is usually quieter. Shade from palm trees provides an escape from the sun, and at the northern end of the beach lie the ruins of Kaneeleele Heiau, an old Hawaiian temple. Amenities: parking (no fee); showers; toilets. Best for: walking.

Those tired of the same old white- or black-sand beaches can lace up good hiking shoes or sneakers to get to this olive-green crescent, one of the most unusual beaches on the island. It lies at the base of Puu O Mahana, at Mahana Bay, where a cinder cone formed during an early eruption of Mauna Loa. The greenish tint is caused by an accumulation of olivine crystals that form in volcanic eruptions. The dry, barren landscape is totally surreal but stunning, as aquamarine waters lap on green sand against reddish cliffs. Drive down to South Point; at the end of the 12-mile paved road, take the road to the left and park at the end. To reach the beach, follow the 2¼-mile coastal trail, which ends in a steep and dangerous descent down the cliffside on an unimproved trail. The hike takes about two hours each way and can get hot and windy, so bring lots of drinking water. Four-wheel-drive vehicles are no longer permitted on the trail. The surf is often rough and swimming can be hazardous due to strong currents, so caution is advised. Amenities: none. Best for: solitude; walking.