This abandoned subway station beneath the Waldorf-Astoria hotel is allegedly used to secretly transport presidents.

This beautiful building in the heart of Manhattan's Financial District was empty for decades.

A crumbling hospital from the 1850s on Roosevelt Island.

The largest 19th century panorama in the world still in-situ.

This historic cemetery was inaccessible for several years due to dozens of land mines.

The place where World War I began.

A vast Communist-era exhibition space in the Bulgarian capital.

"Unity, Creativity, Beauty."

Eastern Bloc nostalgia, anybody?

A collection of art from Bulgaria's time as a communist state.

A striking symbol of the Bulgarian capital.

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

There is a mouldering Jewish cemetery hidden away in the capital of Moldova.

The deepest metro station in the world.

One of the largest museums in Ukraine remembers the story of the German-Soviet War in iconic, brutalist style.

When you've got to go, you've got to go.

340-foot statue built to honour the Heroes of the Soviet Union.

Ruins of a late 1950s Polish ski jump ramp in the middle of the city.

A tribute to the Polish insurgents who fought in the failed attempt to end their city's Nazi occupation.

A hidden art gallery in an abandoned Warsaw fort.

Warsaw's fantastically preserved gasworks...almost.

After the famous composer died in Paris, his sister snuck his heart out of the country to honor his wish that it be buried in their native country.