Rare natural formations: basalt columns, sinkholes, painted deserts, hidden gorges. 17 so far.
The lowest point in Africa, a lake ten times saltier than the sea, ringed by a blinding crust of salt and black lava at the bottom of the Afar rift.
The Eye of the Sahara: a 40 km bullseye of concentric rock rings in the Mauritanian desert, visible from orbit and almost invisible from the ground, which is exactly why hardly anyone goes.
A narrow gorge in the Gobi where a field of ice survives most of the summer in the shade of 200 m walls, with lammergeiers overhead and pikas underfoot.
A salt-dome island in the Strait of Hormuz whose soil comes in seventy colours, with a red beach that stains the sea, rainbow valleys and a 16th-century Portuguese fort.
Caverns of swirled blue-and-white marble carved by waves into the shore of General Carrera lake, reached by small boat from a village on the Carretera Austral.