An overlooked marble is the only surviving in-place 18th century example of the measurement that changed how we define distance.

This Parisian fountain is a little bit fantasy and a little bit nightclub.

The once forbidden "secret cabinet" of erotic art from excavations of Pompeii and Herculaneum.

"There's nothing there," and other lies the KGB told us.

The doodles of a genius line the walls of a secret room under the Medici Chapel, where they were hidden for nearly 500 years.

Murals of the wild parties once held on the frozen River Thames.

The cedar tree in Highgate Cemetery earned its title by accident.

Ship-sized kinetic sculptural fantasy.

London's last remaining public soapbox site has seen speeches from Karl Marx, Vladmir Lenin, and George Orwell.

A makeshift shrine to the late rock star is still kept up on the nondescript façade outside 1 Logan Place.

Thanks to modern navigational tools we now know that the true prime meridian runs through a park next door.

An incarceration museum on the spot of possibly the oldest prison in England.

A collection dedicated to the treatment of disease, held in London's oldest hospital.

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

A special shop catering to the needs of things that go bump in the night, and also helps kids become writers.

In this cobwebbed old operating theater, you can practically hear the screams of the unanesthetized patients.

A subterranean ice warehouse that has lain hidden beneath central London for over a century is now open to the public.