A marvel of Byzantine engineering under the streets of Istanbul.

The "Prussian Versailles" that is as glorious today as when it was built.

A theatre built to house the rowdy Oxford graduation ceremonies became the stage for a debate about God's existence.

One of Europe's oldest libraries.

This narrow Ghent alleyway is an officially sanctioned street art tunnel.

This fairytale castle was built as a show of power but was nearly torn down thanks to its history of torture.

Christ's blood allegedly preserved in a Belgian town.

Brussels' favorite peeing boy has a sister.

A little sculpture with a large wardrobe.

This collection of over 50 murals celebrates Brussels' rich history as the self-proclaimed home of the "comic strip."

Three floors of musical instruments coming from all corners of the world and hundreds of years of musical history.

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

Berlin's beloved bear is immortalized at the Museum für Naturkunde.

Metro station with a claim to rock n' roll fame.

Cold war icon and onetime "hole" in the iron curtain.

One of downtown Berlin's last reminders of its Communist past.

Berlin's natural history museum houses the world's largest mounted dinosaur and the late beloved polar bear Knut.

Thousands of coffin-like pillars make up this controversial Holocaust memorial.

The largest free-standing aquarium in the world resides in a hotel lobby in Berlin.

The most visited, and possibly most controversial, museum in Germany.

An enormous and lavish Gothic church in Czechia.

The slender brass strip in Prague's Old Town Square was used to tell time from 1652 to 1918.

A turn of the century building boasting some of the most beautiful art nouveau architecture in Prague.

This tipsy office building in downtown Prague was originally called “Fred and Ginger.”