These official units of measurement—including chains and perches—lie hidden beneath tourists' feet in a popular London hub.

This ancient Egyptian obelisk still bears the wounds of World War I.

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

Graffiti from the 16th and 17th centuries cover the walls of this part of the Tower of London.

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

The commemorative stone column conceals a secret laboratory.

This incredible collection of vintage pinball machines can be played at 25 cents a pop.

A collection of haunted objects and macabre oddities under one roof.

One of the world's tallest Ferris wheels takes visitors high above Las Vegas in a spinning party room.

This island castle contains enough secret passageways to support a season of Scooby-Doo episodes.

This tiny little island has, as the name says, just enough room for its single house.

NYC's legendary underground network for bovine transportation.

There are owls with glowing eyes in Herald Square.

The 28-foot granite map plots the locations of 40 theaters in New York City.

A pedestrian island in the middle of world-famous Times Square emits a strange (and purposeful) humming noise.

This titanic steel chain linking two buildings was installed without permission but instantly beloved.

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

A bit of retro transportation flair preserved in the world's largest department store.

The New York hotel where tragic visionary Nikola Tesla spent his final hours, destitute and alone but for the pigeons.

A grand New York post office that is home to mailman Santas, scraps of postal history, and a pneumatic mail system.

This psychedelic tromp l'oeil seems to be beckoning drivers to crash into a wall.

The world's largest fire hydrant is supposedly tornado-proof.

A giant cat slowly prowls the parking lot of Zebulon's car dealerships.

A small storefront museum explores the history and myth of West Virginia's famous urban legend.