Blue Grotto
> Location: Italy
Visitors can access this legendary location on the island of Capri off the coast of Naples by wooden rowboat – but only in calm seas at low tide. Inside, it’s almost completely dark. The cavern is only lit by azure blue light from the water – a crystalline blue with silver reflections.
Hang Sơn Đoòng
> Location: Vietnam
If measured by cross-section, Hang Sơn Đoòng – in Phong Nha-Kẻ Bàng National Park, in Quảng Bình Province – is the biggest cave in the world. It was discovered in 2009 and opened to the public four years later. The cave is known for having underground rainforests.
Mendenhall Glacier Caves
> Location: Alaska, USA
Inside a partially hollow 12-mile long glacier, the Mendenhall Ice Caves near Juneau are only accessible by first kayaking to the edge, then climbing over the glacier. Fast-rising ocean temperatures in recent decades have contributed to the glacier receding by almost two miles since 1958.
Pak Ou Caves
> Location: Laos
The Pak Ou Caves are a religious site, containing hundreds of statues of the Buddha. Local legend has it the caves were discovered in the 16th century and have been used for worship since then.
Grutas de Cacahuamilpa Caverns
> Location: Mexico
Getting into these caverns – which form one of the world’s largest cave systems – requires a hike of over a mile. Cacahuamilpa is a “live” cave, meaning that water is still seeping into the formation.
