Xul Solar was an artist of alternate worlds, inventor of languages, and dreamer of utopias.

A gateway to a mysterious network of underground tunnels.

These hut foundations are believed to be the residence of Romulus, founder of Rome.

Classical ruins that remember ancient Rome's presence in Africa.

An Irish Memorial commemorating those who perished due to potato blight.

A tiny, unmarked beer and whiskey bar above an Ethiopian restaurant in West Philly fails to conceal live bluegrass.

A clone-tree in Washington Square Park sprung from seeds that went to the Moon and back.

This Philly cemetery is the eternal home of many famous area residents, including Rocky Balboa's wife.

This little-known collection holds everything from "Dracula" notes, to the manuscript of "Ulysses," to the forged works of Shakespeare.

Frank Lloyd Wright's most iconic home dangles over a Pennsylvania waterfall.

America's most famous museum of medical oddities is home to the remains of Albert Einstein's brain.

This beautiful eden was once the vacation home of Tahitian royals before Marlon Brando bought it.

Perhaps the most beautiful of preserved saints, with a little help from Paris.

Where condemned pirates met their grisly end at the gallows on the River Thames.

This overlooked street light once served as a KGB dead letter box.

A labyrinth hides in plain sight at each of the city's 270 Tube stations.

The watery entrance for condemned prisoners heading to the Tower of London is still visible along the Thames.

This museum tucked below a charming cafe gives a brief snapshot of photographic history.

A Victorian park cemetery, standing on the site of what was once the Great North Wood.

Pop culture has helped to keep this iconic British building from being destroyed.

A 6th-century stone lies at the site of the mythical battle waged between King Arthur and his nemesis Mordred.

The television series' iconic giant foot was borrowed from this classical painting.

A tongue-in-cheek arcade where the games are based on everyday life.

The atmospheric road was never meant to be so creepy.