A curious carving hides on a marble column in the Mosque-Cathedral of Córdoba.

Where commuters walk through remnants of an ancient Greek necropolis.

This ancient Greek place of assembly and marketplace is being revealed layer by layer below the modern Athens cityscape.

World's first "penitentiary," meant to be humane, drove men insane.

A luxurious 1880s hotel with its fair share of Tiffany stained glass, Edison electricity, and of course, ghosts.

Former villa and estate of James Deering developed to preserve native tropical forests.

Japanese gardens dedicated to the Japanese farmer that refused to throw in the trowel.

A semi-scholarly approach to sex.

Elevated freight railway turned wildly successful urban park.

The former home of the Nobel Prize-winning American writer is now home to dozens of six-toed cats.

The unbelievably opulent home built for an infamous newspaperman.

Relics of the 1894 Midwinter Exposition continue to delight visitors today.

After much poking and prodding, this island is decidedly not a magnetic anomaly, but it sure is pretty.

Pagan monument converted to Christianity with the population.

An ancient and majestic fortress that played an integral role in Portugal's road to independence.

This unreal Portuguese palace looks as though it's made from a pile of different castles.

This eccentrically decorated palace is replete with grottoes, fountains, tunnels, and caves.

A 16th century chapel decorated with bones, skulls, and entire bodies hanging from the wall.

A nearly 500-year-old sculpture depicts a man eating a sack of babies, and no one is sure why.

This chimerical bridge/tunnel appears to dead end right into the sea.

It houses the remains of a 17th-century version of the Titanic.

This Slovak bridge is known both for its connection to a national uprising and its UFO-shaped eatery.

This Slovakian statue of an emerging sewer worker might just be a bronze peeping tom.

This Costa Rican topiary park is a surreal garden of unearthly delights.