Home to nearly a third of the world's mud volcanoes, Azerbaijan is home to a messy, bubbling, and sometimes explosive landscape.

Pompeii's less famous neighbor is still revealing her secrets.

An underground paleo-Christian burial site composed of the remains of several cemeteries and Basilicas.

An Italian crevasse filled with abandoned buildings gives visitors a look at the world without humans.

The glowing blue Nymphaeum of Emperor Tiberius.

A submerged archeological park still holds the wonders of a Roman Sodom.

A sulfuric hellscape in southern Italy.

Mount Nyiragongo has erupted at least 34 times since 1882 and is home to the world's largest lava lake.

Over two-thirds of the world's population of giant tortoises live among this coral formation.

Once living up to its name as the grandest hotel in all of Africa, the Grande Hotel is now home to a community of squatters.

Fabulous formations, weird and wonderful wildlife.

The centuries-old trees lining both sides of this dirt road may become Madagascar's first natural monument.

A South African bar inside a hollowed out 6,000-year-old Baobab.

An Ethiopian "Jerusalem" featuring a church hewn out of a single rock.

An ancient Ethiopian cave church is endangered by the simple building of a road.

An ocean in the making, in the Ethiopian desert.

A salt lake dotted with steaming limestone chimneys.

Keshwa chaca, among the last handwoven Incan bridges, crosses Apurimac Canyon in Peru.

An underground city of salt.

The largest hewn stone in history.

Remains of an abandoned coral city.

Village of slate houses, built on a white marble outcrop.

One of the largest ancient geoglyphs in the world is a tall desert god used for predicting the weather.

Ethiopian standing stones featuring remarkably preserved carvings of swords and people.