A 16th-century monastery boasts a lush array of plants native to Mexico’s most biodiverse region.

An ancient Viking runestone hidden in plain view in Stockholm's old town.

There is only one place in the world where the corners of four nations come together.

A mysterious pillar in an ancient burial chamber is said to predict how long you have to live.

The world's second largest single-dish radio telescope, once used to contact E.T.

This bleach-white graveyard overlooking the ocean is accessed through a tunnel.

The ancient latrines of the Greeks, in all their public glory.

This wonky bit of historical taxidermy is experiencing a second life online.

A small etching on the white marble parapet was written in runic script by a Viking mercenary.

Stone carvings record the Norse myth of Sigurd, providing a glimpse into Scandinavia's transition from paganism to Christianity.

Home to three historic ships from the age of Vikings.

For six months of the year, three giant mirrors direct a pool of sunshine onto this otherwise occluded town.

London's last remaining public soapbox site has seen speeches from Karl Marx, Vladmir Lenin, and George Orwell.

A unique tribute to the millions of animals who served and died for the British military.

Live a night as a Byzantine King, with a minibar and private jacuzzi.

The deepest underground city in Turkey was designed to protect 20,000 people behind massive stone doors.

In this historic region, homes and churches are carved into ancient volcanic rock formations.

The mysterious 855-foot zigzagging stone wall has been baffling people for centuries.

The ruins of New Zealand's largest classical-style church.

A New England-style lighthouse along California's beautiful Highway 1 gets a re-do.

This small monument marks the divide between the Atlantic and Indian Oceans at the southernmost tip of Africa.

A series of waterfalls so massive they straddle the border of Argentina and Brazil.

A brightly colored natural bridge formed by mineral-rich hot springs high up in the Andes.

Clap your hands at the base of the pyramid, and the song of a sacred Mayan bird will echo through the air.