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

The John Snow Memorial marks the epicenter of London's 1854 cholera epidemic.

England's most famous front door has an accidental doppelganger.

These ornate arches show how the course of the River Thames has changed.

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

Largest lake in Great Britain measured by surface area.

A remarkable feat of Victorian engineering across the Firth of Forth.

Old-fashioned knowledge and modern engineering create the world's only rotating boatlift.

Edinburgh's oldest statue hides within a parking lot behind the city's iconic cathedral.

This alley off Edinburgh's Royal Mile contains remnants of the city's seedier history.

The fountain marks the area where hundreds of accused witches were burned at the stake.

17th century streets hidden under Edinburgh were once a breeding ground for the black death.

The ruins of the largest gladiatorial school in Rome are largely hidden under modern streets.

One of the world's tallest statues is also one of its most hated.

Overlooked by many, the two famous Scottish warriors guard the main gate of Edinburgh Castle.

The oldest residential street in Europe also features an optical illusion.

The commemorative stone column conceals a secret laboratory.

This massive collection of British military artifacts includes the heartbreaking personal letters of the men in the trenches of WWI.

Visit a surreal landscape so otherworldly NASA actually used it to train the Apollo 17 crew.

The ruined abbey includes a rare surviving example of a monastic latrine.

Revel in the Victorian splendor of the world's oldest eating establishment inside a museum.

A sculpture made of 10 Cadillacs as a monument to the "Golden Age" of the American automobile.

Once one of the largest rooms full of books in the world, this bookstore basement is still a treat for bibliophiles.

Electrical pylon in the shape of Disney's beloved mouse.