A historic London pub with prison cells in the cellar and a "spy room" on the second floor.

The site of London’s first coffee house has been serving refreshments of one kind or another for 360 years.

Rebuilt remains of a temple to Roman god Mithras.

A charming 17th-century alley is lined with secondhand bookstores and antiquarian shops.

This churchyard arbor is surrounded by hundreds of gravestones placed there by author Thomas Hardy.

The Cimetière des Chiens et Autres Animaux Domestiques is one of the oldest pet cemeteries in the world.

The video game-themed street art first popped up in the French city.

A mud statue stands in the dark tunnels, seeming to hold up the weight of the city above.

This life-size replica of the Statue of Liberty's flame is also a tribute to Princess Diana by default.

The water-powered carriages are long gone, but for over a century this funicular railway has been the fastest route to the highest point in Paris.

A museum on the history of Paris, including a set of Napoleon's toiletries, Proust's room, and relics of the Revolution.

Indents in the pavement are all that remain from a grisly death machine in Paris.

Site of a classic 19th-century physics experiment to prove the earth is rotating.

This statue was given to France by the United States to commemorate the centennial of the French Revolution.

France's national museum of scientific and industrial instruments.

This charming cobbled backstreet is the most Instagramable street in Paris, much to the residents' annoyance.

Notorious artist squat renovated into legal studios.

Seventy-five miles of limestone caves host more than a million bottles of wine beneath a sleepy Moldovan town.

A unique collection of Soviet military artifacts lies hidden away in a disused train, in the unrecognized Eastern European republic of Transnistria.

This abandoned Soviet circus is slowly being restored to its Communist-era glory.

A Bulgarian monument to Russia's role in World War II is constantly being painted in pop culture protest.

An abandoned saucer-shaped monument in the Bulgarian mountains.

This Ukraine alleyway has become its own little island of forgotten things.

The largest collection of death masks in Ukraine.