Apartment complexes built into huge repurposed natural gas tanks.

Dine amidst exotic plants at this former royal greenhouse.

Vienna's underworld of tunnels and subterranean rivers made an iconic appearance in a 1949 Orson Welles film.

Beautiful Austrian natural history museum with carved ceilings and row after row of ancient taxidermy.

This cubist Vienna church building looks like some sort of alien stonehenge.

A top-secret bunker now turned museum, is an eerie look at what life would have looked like in the event of nuclear war.

This inconspicuous pharmacy went down in history as the first gas station in the world after fueling the first road trip ever taken.

This baroque palace displays an impressive collection of taxidermy, art, and rare objects from the days of courtly hunting.

One of the largest busts in the world celebrates the German city's erstwhile namesake.

An abandoned Art Deco hotel nestled on the side of a wooded mountain.

The ruins of a former sanctuary for elite Aztec warriors.

The remains of the great moral philosopher reside in a university in London.

One of the few remaining casualties of the London Blitz, this destroyed church has become an enchanting public garden.

The dramatic remains of an abandoned farmhouse sit high on the edge of a remote hillside.

A World War II torpedo launch station abandoned off the Polish coast.

The housing complex served as an anti-fascist fortress during the Austrian Civil War.

The former global standard for the exact mass of one kilogram sits under lock and key outside Paris.

A fantastical 13th-century fortification sandwiched by a modern hotel in central Brussels.

Cozy basement bar sports an inventory of over 2,000 beers.

When you're a great Russian Tsar, even your vomit gets a statue.

Theme park featuring miniature replicas of European monuments.

Climb inside an iron crystal magnified 165 billion times its normal size.

Lavish royal estate punctuated with heated greenhouses.

The Belgian royal family's private depot now stands abandoned and forgotten alongside the tracks.