An alchemist's "magic door" stands in the middle of a Roman park.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

A backdoor to Machu Picchu that only the most foolhardy infiltrator would attempt to breach.

The world’s highest ski resort was deserted after an 18,000-year-old glacier melted away.

An old limestone mine transformed into a beautiful and unusual sculpture museum.

A subterranean relic of the Spanish Civil War hides below this picturesque park.

Hundreds of enormous icebergs drift through this waterway every year.

Thousands of acres of beautiful wild landscape in the Great Basin.

Nearly 300,000 acres of wildlife, natural splendor, and a hidden ghost town have been designated a national monument.

A collision of human error and natural geothermal pressure created this rainbow-colored geologic wonder.

The "Bridge Over the Atlantic" lets you cross the waterway in mere seconds.

The hidden ruins of an old hydroelectric plant reclaimed by nature.

These medieval funerary monuments are now home to a colony of critically endangered vultures.

This 16th-century mosque is the hallmark of the African architectural legacy in India.

An otherworldly, fossil-rich cobble beach holds Viking graves, cairns, and other remains.

This colorful palace is an oasis of calm amid the hustle and bustle of the Buriganga riverfront.

Only a fragment of this 15th-century Dance of Death survives today.

Step into a cartoon at this Seoul café that aims to evoke a two-dimensional scene.

One of the few remaining examples of 19th-century London’s attempt to clean up its reputation.

Tens of thousands of ancient rock carvings hidden in the heart of a French national park.

The ruins of an ancient pyramid built by the mysterious Chupícuaro civilization.

The last occupied troglodyte dwellings in England weren't abandoned until the 1960s.

This 8th-century Bavarian monastery is home to an exquisite Baroque-era library.

This landmark Victorian folly rewards visitors with spectacular views over the Peak District.