The bones of prehistoric animals and early signs of human habitation have been found inside Malta's "cave of darkness."

Despite the name, these small saltwater swimming pools have nothing to do with the Romans.

These wire animal sculptures commemorate the exotic inhabitants that once called the Tower of London home.

This Balinese sea temple is thought to be guarded by the hundreds of monkeys that live around it.

Once a meeting point for great thinkers, and the midpoint of the country.

For 200 years, people have flocked to this Polish town to experience the healing powers of salt.

For centuries, this hill along the Polish coast has been used as a lookout—and the rumored home of pirate treasure.

This 16th-century pole was once used in brutal public executions.

This ancient Roman aqueduct once funneled water to Diocletian's palace.

You can still ride this 100-year-old work of art in Brooklyn's largest public park.

A tree that grows parallel to the ground was declared Brooklyn's "crowning curio" by the poet who saved it.

This elaborate tunnel is the first structure composed of cast concrete in the United States.

A vibrant, 100-foot-tall mural dedicated to Evelyn Nesbit, the tragic icon of the Gilded Age.

A Pythagorean funhouse that tries, successfully, to prove that math is the coolest thing ever.

Nature puts on a spectacular show at this blowhole on the eastern side of Gran Canaria.

Study the Alien etchings in this fountain while you refill your water bottle.

Commemorating the spot where the famous scientist fed his pigeons.

The fanciest public restroom in New York City boasts fresh flowers, art, and a classical music soundtrack.

Fake subway tiles were installed to cover a design that resembled the Confederate flag—it's unclear if the resemblance was intentional.

This historic address is home to the beloved ball and is an almost totally empty building among the most expensive real estate in the world.

There must be a pun in this haystack somewhere...

The origins of midtown Manhattan's anachronistic wooden farmhouse remain a mystery.

Built hundreds of years ago this downtown iron barrier once protected a much despised king.

Currently housing a corporate bank branch this building at the southern tip of Manhattan was once the gateway to luxury vacationing.