The giant statue and its model solar system honor the native Pole who declared that the Earth revolves around the Sun.

This biographical museum honors the groundbreaking scientist at her birthplace in Warsaw.

A statue honors the children who fought Nazis in Poland.

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

While this monument tile is shrouded in mystery it also marks the end of the longest ever human chain.

Travelers who fall victim to this mermaid's charms are destined to stay in Užupis forever.

This micro-nation may be some sort of prank, but its constitution sure seems official.

An old hill fort covered in over 100,000 crosses is a symbol of Lithuanian nationalism and beliefs.

Built to ward off Napoleon's army, this city-sized abandoned Russian fort is now perfect for urban exploration.

A black cat protests the City Guild in Riga's Old Town.

This real life asylum of horrors is now an abandoned ruin that hides the unbreakable code to one patient's insanity.

This ritzy Italian market is built around a statue of an unforgiven heretic who was burned for his belief in an endless universe.

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

Explore this medieval cathedral by trying to spot all the malevolent monsters hiding in its beautifully colored windows.

There has been an astronomical clock on this spot since the 14th century.

This bridge was constructed from the rubble of the infamous Bastille.

Paris' linguistic guide to the international language of, yes, love.

A subterranean house of worship carved right out of the bedrock.

This irregularly shaped sea fortress has defended not one but three different sovereign states.

A cathedral resurrected from the ashes of one of Europe's greatest urban fires.

The Guardian of Tallinn.

Disused seaplane hangar gets a second life as the jaw-dropping home of Estonia's museum of maritime history.

A statue of the Soviet leader still stands in a quiet corner of Estonia’s most Russian city.

Four alabaster giants contemplate the tides on the shore of Denmark.