This remote, abandoned Soviet observatory promises spectacular views for those who can reach it.

These morbid carvings remind churchgoers of the inevitability of death.

Where condemned pirates met their grisly end at the gallows on the River Thames.

A relic of Victorian grandeur hides beneath a busy South London road.

Tombstones and enigmatic inscriptions hide within a vault beneath a popular London arts venue.

The first tunnel to be dug beneath a river, repurposed as an art and museum space.

This landmark church concealed a crypt packed with bones that was discovered thanks to the London Blitz.

A historic London cemetery now serves as a nature park incorporating gravestones & memorial statues.

The remains of Crystal Palace Great Exhibition of 1851.

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

A horde of stray cats rule in this secluded Parisian cemetery under a bridge.

The best preserved Paleochristian basilica in Rome hides a number of oddities and secrets.

An endless sea of white conical domes.

Ozymandias’ time-keeping temple.

These Egyptian statues have survived for 3,400 years and were an acoustic wonder of the ancient world.

A museum in the childhood house of a medical pioneer.

The avant-garde design was able to bypass strict Soviet regulations on architecture.

An abandoned swimming pool decays on the outskirts of Berlin.

A unique Holocaust memorial tells the personal stories of the Jewish residents exiled from greater Berlin.

Started as a kitchen garden, now the second largest botanical garden in the world.

A tour of underground Berlin takes you through WWII air raid shelters and tunnels used to smuggle people out of East Germany.

A former squatter's paradise outside Prague.

Serving Central Asian breads that range from cracker-crisp to warm and fluffy, this bakery brings Bukhara to Queens.

The dining hall that nourishes workers in Chernobyl's Exclusion Zone is also open to visitors.