A monument to the three wars that led to German unification towers within a Berlin traffic circle.

This historic streetcar system has been running since the 19th-century.

One of the most beautiful bookstores in the world hides a neo-Gothic interior behind an art nouveau facade.

Once the fallout shelter of a dictator, this sprawling bunker is now a combined history museum and contemporary art gallery.

In the heart of Tirana, this underground nuclear bunker has been transformed into a museum.

A museum dedicated to secret surveillance.

Bronzes and busts that once stood in the city's main squares are now relegated to a small hidden courtyard.

An Albanian monument to the Communism that nearly crushed the country is now a crumbling wreck.

A shining memorial to a Belgian hero is said to bring luck to anyone who touches it.

A little sculpture with a large wardrobe.

These slanted cubic abodes are a creative if odd solution to a zoning pickle.

Europe's official "zero-level," the equator of elevation.

The attic of a four-century-old canal house hides a clandestine church.

Amsterdam's narrowest house facade is a monument to 17th-century tax evasion.

This cheese shop also houses a museum devoted to Dutch dairy.

Tucked in the back of a flower shop, its collection details the fascinating history of the Netherlands's iconic symbol.

This Netherlands museum holds a gloriously mechanical collection of ornate musical automata.

Underground attraction offering tours of the foundational ruins of a church nave that collapsed in 1674.

Incredible labyrinth of man made caves.

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

Gaudí's famously flamboyant architectural style is on full display in this sprawling park and garden.

Step inside the first house designed by Catalan architect Antoni Gaudí, considered to be one of the first Art Nouveau buildings.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

A vista of the city and sea from atop the little-known viewing deck on an unassuming Columbus statue.