A museum dedicated to a secret military hospital hidden beneath a castle in Budapest.

A trail of iron footwear stands as a monument to the thousands executed along this riverbank during WWII.

A random tree outside a Budapest hotel has become a DIY shrine to the late singer.

This sculpture honors the man who was known as the "Righteous Among the Nations."

The metal leaves on this tree are engraved with the names of Holocaust victims.

The holes in this wall provide a glimpse into Jewish life in Budapest, both past and present.

Budapest's Communist-era statues, banished to the suburbs.

Uh, pardon me, ma'am, but I couldn't help noticing that there's a Columbo statue in the middle of Budapest.

This memorial complex contains several mass graves for victims of the Siege of Leningrad.

Palace where the nearly un-killable Rasputin was murdered.

Inside the world's largest seed bank, WWII botanists elected to starve to death rather than compromise their collection.

A 250-year-old timepiece-automaton adorned with golden mechanical birds, which still sing to this day.

Perhaps the tiniest sculpture in Saint Petersburg is a little bronze finch inspired by a song.

Gargantuan home of Russian science.

This newly renovated Soviet-era outdoor exhibition center is bigger than the principality of Monaco.

Museum celebrating the achievements of the Soviet space program.

Moscow's imposing monument to the Space Age.

A 360 degree battlefield experience.

This massive monument honors the first human in space.

A sculpture park of the tossed aside relics of the USSR, from Stalin to a massive Soviet emblem.

The gorgeous entrances into the city's underbelly look more like grand halls than subway stops.

The tallest hotel in Europe.

One of the world's tallest statues is also one of its most hated.

Former headquarters of the KGB.