In the Valley of Morelos lies a mysterious Olmec site with signs of jaguar veneration.

This centuries-old hotel hides a network of secret cellars and passages once used by smugglers.

A tunnel with windows, so you don't miss out on the impressive views.

This Roman underground canal was the longest tunnel ever built until the late 19th-century.

This scenic fortress dates back at least 2,400 years to the time of Magna Graecia.

This lesser-known leaning tower is all that remains of the medieval castle of Vernazzano.

This beautiful, all-in-one museum, private residence, and bed and breakfast houses a rich collection of African art.

This semi-spooky remnant of an abandoned hotel provides fantastic views.

The former home of a conniving 17th century politician is now a high-end hotel.

Centuries of warfare, tragedy, executions, and poetry come together in this 13th-century fortress.

Designed by Horace Trumbauer in 1893, this Gothic-style castle is now a home for academics.

This abandoned bridge is now a favorite haunt for graffiti artists.

The world's longest bridge fountain has hundreds of nozzles that create a beautiful, illuminated spectacle.

An opulent testament to the boom-and-bust history of industry in north central Indiana.

A remarkably opulent mansion with a tragic history.

A 19th-century British industrialist built this Louis XIII–inspired chateau for his homesick French wife.

This New York estate was designed to resemble a medieval Scottish castle.

This twice-relocated "Usonian" home is among the smallest built by master architect Frank Lloyd Wright.

The precise origins of this pink sandstone temple are unknown.

What started as a way to address damp basement walls turned into a house filled with intricate hand-carved designs.

Although it has never been a secret ninja base, this shrine still has plenty of tricks up its sleeve.

This home designed for chocolate magnate Antoni Amatller is an exquisite treasure-box of Catalan Modernism.

This stunning sea creature-shaped home blends into the landscape like a fantasy villa.

An unremarkable wooden wheel built into the side of one of Rome's oldest hospitals was part of a policy to reduce infant exposure.