The only swimming pool listed on the National Register of Historic Places is emptied and refilled each day with naturally filtered water.

Built as a gift to the hottest tastemaker of the time, these hidden quarters remain an Art Deco showpiece.

During the 17th-century, orphaned infants were placed in this barrel to be cared for by the hospital.

Enjoy the waters of this half-moon-shaped natural pool surrounded by breathtaking scenery.

This beachside town is home to a diverse nature reserve, multiple cays, and one of the three bioluminescent bays in Puerto Rico.

A uniquely lettered street sign marks the corner where the iconic word game was invented.

The remains of Crystal Palace Great Exhibition of 1851.

This bridge made famous in a novel and on-screen wasn't actually built over the river Kwai.

A 2,000-ton rock resting in a state of a delicate balance.

This imposing tower named after the mythical sword of King Arthur is considered the tallest freestanding climbing wall in the world.

It should come as no surprise that the best view of the Hollywood sign is from Batman's lair.

A boulder in the Churchyard of Down Cathedral marks the legendary burial place of "The Apostle of Ireland."

This rare and ancient Christian relic is one of Ireland’s oldest freestanding stone crosses.

The hermits of Karoulia protect their asocial lifestyles by living on the vertical face of a treacherous precipice.

This lovely university observatory continues to sit abandoned since its potential savior was sent to jail for fraud.

The longest continuous lava tube in the continental U.S. offers 2.5 miles of dark explorations for the adventurous.

At night, bats patrol this magnificent 18th-century space in search of book-eating pests.

A heated statue pays tribute to one of Sweden's great actresses.

A statue of the legendary Celtic warrior queen who fought the Roman invaders stands in one of the cities she once destroyed.

Buildings from the fictional planet of Tatooine still litter the Tunisian desert.

Here, at the "world's longest art gallery," you'll find forty miles of ancient petroglyphs and pictographs.

The location of the world's first telescope demonstration.

The floor of this spectacular Baroque sanctuary is covered in memento mori.

Ferdinand Magellan dubbed the world's largest water village the "Venice of the East."