Catacombs turned marketplace.

A little slice of Japan and its aesthetics in London's Holland Park.

A 1,215-foot tunnel transports pedestrians beneath the River Thames.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

This charming colonial alleyway is one of the oldest continuously used residential streets in the U.S.

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

Mural made of 100,000 pieces of hand blown glass, and until recently, the largest glass mural in the US.

Tour the dark and beloved poet's former cobwebbed basement, which may have inspired "The Black Cat."

A rare view of a preserved Victorian science museum.

This beloved marketplace mascot poops money and grants good luck.

This elaborate towering structure was once famed for its revolutionary height.

Golden and naked, the figure that was once the highest point in New York is all that remains of the second Madison Square Garden.

Yo, Adrian!

Dr Barnes' $25 billion private collection of art and arboretum.

A rotating cast of guys and dolls in front of a Washington, D.C. building.

A group of abandoned factories and buildings that have been revitalized and are now used to promote culture, education, entrepreneurialism, and sustainable development.

This mosaic dedicated to John Lennon was tended for years by a Beatles super-fan.

New York City's smallest piece of private property.

This whimsical group of statues is a favorite of children who love to climb all over Lewis Carroll's beloved characters.

Whisper secrets in a busy station only to be heard on the other side of this acoustic arch.

Try not to get slimed in Tribeca.

The medieval center of the Islamic world was also once the seat of Saladin's sultanate.

Ancient Egyptian relief, claimed to depict an electrical light.

Some believe that this ancient mural depicts technology far ahead of its time, but in reality it's nothing quite out of place.