Drift by boat beneath a cave ceiling lit by thousands of glowworms.
Wind-carved chalk mushrooms and icebergs of rock glowing at sunset — camp overnight under the Sahara stars.
Baltic island of rauk sea stacks and the Hanseatic walled town of Visby.
Home of Son Doong, the world’s largest cave, plus Paradise Cave and boat trips into the river cave of Phong Nha itself.
Rift-valley site of the world’s oldest parliament, where the tectonic plates pull apart.
Rainbow-striped Andean valley of adobe villages in Argentina’s far northwest.
Drift between the American and Eurasian tectonic plates in gin-clear glacial water.
England’s chalk-white front door: cliff-top paths above the Channel with France visible on a clear day.
Gunung Mulu’s vast cave system, including the Deer Cave and its nightly bat exodus.
Monasteries atop soaring rock pillars.
Rhyolite mountains streaked orange, green and pink, with a natural hot river to soak in after the walk — the start of the Laugavegur trail.
Climb 740 steps up the El Penol monolith for views over a maze of turquoise reservoir lakes.
Mineral springs that have petrified into white waterfalls of stone above the Oaxaca valleys, with cliff-edge pools you can swim in.
Limestone-cliff beach reachable only by longtail boat, and the best rock-climbing spot in Southeast Asia.
The highest tides on Earth, best watched among the Hopewell Rocks flowerpot stacks.
Slot canyon on Navajo land near Page, Arizona, carved into swirling sandstone by flash floods.
See fossilized trees, painted desert badlands, ancient sites, and Triassic landscapes in Petrified Forest National Park.
Descend into vast limestone caves and desert landscapes at Carlsbad Caverns National Park.
See the steep dark cliffs and narrow river-carved gorge of Black Canyon of the Gunnison National Park.
Explore sandstone domes, cliffs, canyons, and the Waterpocket Fold in Capitol Reef National Park.
Infobox
