The somber sculptures commemorating Irish Famine on the river Liffey in Dublin.

A museum that cashes in on its infamous little people while teaching you a thing or two about the Irish fey.

The modern birthplace of Irish freedom.

Though they've since been renamed, these two streets hint at Dublin's darker days.

The oldest public library in Ireland.

The gorgeous library at Trinity College is home to remarkable treasures of Irish identity.

The ruins of this Dutch castle sit atop a labyrinth of once-secret tunnels and passageways, dating back over 900 years.

This centuries-old gothic monster has been converted into a sprawling, glossy bookstore.

A once-magnificent collegiate church is falling into ruin.

The last bastion of Roman presence north of the Alps looms over a German town.

The birthplace of Karl Marx is now a museum dedicated to the communist revolutionary's life and work.

Amsterdam's former hotspot for public executions and dissections.

A hidden church in a hidden courtyard tells the story of the Miracle of Amsterdam.

This historic Amsterdam bar used to accept sailor's monkeys as payment.

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

This memorial commemorating fallen Swiss Guards of the French Revolution has been called the saddest stone in the world.

Go inside to really appreciate this 500-year-old technological masterpiece.

Macabre astrological automaton clock dating to the late 1400s.

This unusual piece of Renaissance art depicting the bodily horror of crucifixion and skin disease may have been inspired by fungus-induced hallucinations.

Go surfing on this urban wave, "hacked" by local surfers.

These bronze pamphlets remember a remarkable group of Germans who fearlessly opposed the Nazis in the very center of their power.

Daily jousts and dancing barrel makers in Munich's mechanical clock.

Beneath the city of Lourdes, France is a massive, concrete church.

An ancient and majestic fortress that played an integral role in Portugal's road to independence.