Here be dragons.

The enormous 250-room Vanderbilt mansion conceals hidden doors and secret passageways.

This downtown Dallas art installation is always on the lookout.

Under the desolate and windswept northern coast of Barbados stands a small oasis filled with sea anemones.

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

Site of a classic 19th-century physics experiment to prove the earth is rotating.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

These mysterious Viking chess pieces spent centuries hidden on a remote Scottish island.

Two large-scale sculptures of Adam and Eve greet visitors in the nude at the Time Warner Center in NYC.

This small fort played a huge role defending Puerto Rico’s capital city.

This otherwise ordinary close on the Royal Mile constituted the end of the world for Edinburgh’s poorest residents.

The fierce beast perches atop a pedestal marking where the historic City of London gates once stood.

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

The Tudor-style cottage in the middle of the square is not quite what it seems.

Originally built for London’s cab drivers, this bright green hut now serves anyone a hot drink or meal.

The "lost friend” is the most famous of the six moai statues that were removed from Easter Island.

The 16th-century church has the only stained glass windows that survived the Scottish Reformation intact.

Touching this 18th-century Scottish philosopher’s toe allegedly conjures good fortune.

New York's southernmost subway station is whimsically wavy.

Islanders once used this dramatic, otherworldly landscape to hide their cattle from Viking raiders.

The dairy farm in upstate New York where nearly half a million people gathered for three days of peace and music in 1969.

These official units of measurement—including chains and perches—lie hidden beneath tourists' feet in a popular London hub.

Legend tells how a Spanish soldier disappeared from this isolated sentry box without a trace.

In the days before house numbers, these colorful signs held clues about various buildings' purposes.