Forest of razor-sharp limestone, UNESCO-listed.
Striped, dome-shaped rock formations.
Sea cave at the island’s northern tip with anemone pools and ocean windows.
Tram tour through a dripstone cavern.
Jagged eroded sandstone ridge.
Red sandstone amphitheatres carved into the coastal plateau north of Pointe-Noire.
Africa’s largest canyon, 160 km long and 550 m deep, with a five-day hike along its floor.
Sacred rock outcrop over Abeokuta.
An underground train runs into 24 km of dripstone halls, home of the blind olm salamander.
A 725-metre monolith with a face-like pattern, on the road to Abuja and on the 100-naira note.
Windmills, spa towns and a meteor crater.
Waterfall dropping through three natural bridges into a cave shaft.
A "mini Grand Canyon" of red rock.
Otherworldly landscape of limestone chimneys.
Sheer desert escarpment near Riyadh.
Young fissure volcano between spreading tectonic rifts.
Spectacular two-level limestone caves.
The one Kenyan park you can explore by bike, pedalling past zebra and giraffe to the red cliffs and gorge that inspired The Lion King.
Karst caves stuffed with Buddhas amid sugarloaf mountains.
Eroded "moon landscape" near the coast.
Climb the vast flat-topped tepui.
One of the largest green canyons on Earth, seen from God’s Window and the Three Rondavels viewpoints.
Bubbling grey cones on the Caspian steppe — half the world’s mud volcanoes are here.
Neon sulphur pools, salt flats 125 m below sea level and the Erta Ale lava lake — the hottest inhabited place on Earth.
Trails and tunnels along a marble canyon so narrow the cliffs nearly touch, with the Eternal Spring Shrine over a waterfall.
Eroded clay badlands a stone’s throw from the city.
Wind-carved kalut ridges in one of the hottest places ever measured on Earth.
Six sapphire lakes held by natural travertine dams in the Hindu Kush — Afghanistan’s first national park.
Sea cave on the Algarve coast with a round skylight in its domed roof — reached by boat, kayak or paddleboard.
Row through limestone karsts and rice paddies on the "Ha Long Bay on land", then climb to the Mua Cave viewpoint.
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