This unassuming bookstore in the heart of Madrid is one of the oldest in Spain.

Over time, this castle grew to encompass the entire island.

The Cathedral of Salamanca has a number of unusual carvings but none so surprising as a modern astronaut.

Built in 1870 at the bridge that connected Buda and Pest, this spectacular incline railway was almost lost forever during World War II.

The facade of this 16th-century building is decorated with carvings of 300 seashells.

This Roman arena once played host to bloody gladiatorial battles.

This enormous monument is one of the most iconic structures in Tokyo, rudely nicknamed "The Golden Turd."

The Roman city was the birthplace of various emperors and is home to one of the empire's most impressive architectural feats.

The discovery of these rare, ancient artifacts led to the creation of a new museum.

A large collection of ancient runestones decorates this university courtyard.

This colossal ancient sculpture of the monstrous Aztec rain god has a literally stormy history.

A lush indoor jungle fills this bustling Madrid transportation hub.

A curious memento mori hangs in the magnificent Cathedral of Segovia.

This enormous censer uses a pulley system installed over 400 years ago.

This Transylvanian church has changed its denomination four times.

Nine centuries-old fortresses guard the walls of this medieval Romanian city.

A surreal statue honoring Prague's favorite literary son.

The most elaborate of 12 medieval arched doorways to the old city of Burgos.

Long tunnels run under the ancient chariot racing circuit to the tower.

The geographical center of Budapest is marked with a 10-foot-tall stylized zero.