A chain of 16 wondrous lakes formed as a result of the gradual dissolution of soluble layers of bedrock.

A marvel of Byzantine engineering under the streets of Istanbul.

Réunion Island's highest point is a two-million-year-old volcano and a paraglider's paradise.

Native Americans built this circle of stones, which was used to predict astronomical events.

Uganda's smallest savannah park is home to over 350 species of birds and mammals.

This center in the Rwandan capital supports women’s livelihoods while educating visitors about traditional cooking, craft making, and more.

In the heart of Luxembourg's "little Switzerland" weaves a breathtaking natural sandstone canyon with a mythological past.

The smaller of the three towers of San Marino is a former prison inaccessible from the ground level.

The secret centuries-old German cemetery in the heart of the Vatican.

Mosaics, storks, and brothels—this ancient city has it all.

Once a favorite playground for the world's most illustrious guests, Hotel Nacional's secret weapons and bunkers reveal a more menacing side to its golden history.

The ancient water tanks remain some of the ruined city’s most beautiful architecture.

The most famous location in China was home to whole dynasties worth of imperial rulers.

Once the most densely populated place in the world, this island is now a ghost town.

Self-mummified monk who wears sunglasses and has become a gecko hatchery.

This ancient monastery complex was transformed from an island to a peninsula when the lake was partially drained.

This Armenian monastery was carved out of cliffs and named after the spear used to stab Jesus.

Nestled in a peaceful valley, this Armenian monastery may have been saved from Mongols thanks to the eyes of God.

Called the "Armenian Stonehenge," this ring of menhirs pierced with holes may be a prehistoric astronomical observatory.

The world's longest nonstop reversible cable car soars through spectacular scenery to the medieval Tatev Monastery.

The most visited pilgrimage site in Armenia once held a saint in a pit for 13 years.

The charmingly disheveled clock tower of Tbilisi's puppet theater.

Bridge that died in war and was resurected.

A statue in the center of Dublin dedicated to one of their favorite sons of rock & roll.