The Māha'ulepu coastline east of Poipū is one of the most geologically unusual landscapes on Kauai. The cliffs here are made of lithified sand dunes — ancient coastal dunes that hardened into stone over thousands of years — and the eroded surfaces contain fossils of Hawaiian birds, many of them species that went extinct after Polynesian settlement. It's a landscape that feels prehistoric even by Hawaiian standards: raw, wind-battered, and largely untouched by development.
Access is via a dirt road through the Grand Hyatt's property (generally open to the public for hiking) or by parking near the beach and walking the coastal trail. The trail along the cliff tops is excellent walking with good views of the rugged coastline, and the rock formations at Māha'ulepu beach itself — stacked, honeycombed with wave action — are striking. Allow two to three hours for the full circuit. Good shoes are essential; the trail is uneven and some sections involve scrambling.