The mortal remains of an estimated 70,000 people lie in the basement of a monastery in Lima, Peru.

Hollywood's most famous landmark, the "temporary" sign that has stood for decades longer than intended.

The glowing blue Nymphaeum of Emperor Tiberius.

A bizarre roadside attraction and the first instance of miniature golf in the world.

Home to the largest urban bat colony in North America, estimated at 1.5 million bats.

The last moments of the ill-fated Pompeiians, frozen forever in plaster.

The second-largest cave chamber in the world was discovered in 1898 by a 16-year-old and a friend known as "Pothead."

Ruined 11th century abbey built by King David I in Edinburgh, Scotland.

An unusual round church in London with a Templar past.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

The hallucinogenic center of the ancient world.

Tour the dark and beloved poet's former cobwebbed basement, which may have inspired "The Black Cat."

The gorgeous library at Trinity College is home to remarkable treasures of Irish identity.

Kings Cross Station pays tribute to its role in Britain's best-selling book series.

A hands-off space for graffiti artists to hone and display their skills.

A museum dedicated to the alleged Roswell Incident.

The ancient dwellings of the Puebloans, located in the cliffs of majestic mesas.

Famously misunderstood wonder of the ancient world

This 4,000-foot-diameter hole is touted as "the most well known, best preserved meteorite crater on Earth."

Northern Ireland's Brobdingnagian stepping stones.

The fairy tale castle of the "fairy-tale king."

The intricate stonework of Machu Picchu serves as a testament to Incan engineers.

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