The beautiful, ornate weather station is the most popular geocache in Salzburg.

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

This city square is home to Amsterdam's oldest church and a statue honoring Dutch sex workers.

These spartan apartments are provided to clergymen visiting Vatican City.

Historic fortifications form the boundary of Vatican City, but it’s not entirely surrounded by walls.

This is the largest cemetery in Ireland and the first cemetery museum in the world.

One of Ireland's most infamous prisons for rebels including men, women and children.

Eighty million natural history specimens call this gargantuan museum home.

Five candy-colored villages on the Italian Riviera.

Two stone columns flank the grand Venice square, but there were supposed to be three.

Venice's "Island of the Mad."

In Rome’s Jewish ghetto, a 200-year-old bakery still makes the neighborhood’s historic sweets.

2300-year-old Roman road connecting the empire.

The world's largest reflecting pool is just two centimeters deep.

The video game-themed street art first popped up in the French city.

A short distance from the Eiffel Tower is the final resting place of several of the city’s more well-known and interesting characters.

The tradition of open-air secondhand and antiquarian bookselling in Paris dates back to the Renaissance.

High atop the Eiffel Tower is a small apartment built exclusively to entertain the science elite and make the rest of Paris jealous.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

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

Ring the bell to enter a bar that looks equal parts museum and old curiosity shop.

The iconic boulevard is the perfect place to catch sight of a bicycling skeleton, a levitating Satan, or a chef with his head stuck in a pizza.

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

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