The palace window through which Protestant nobles flung two Catholic regents, thus sparking the Thirty Years' War.

This easily overlooked memorial immortalizes the scars from the 1956 Hungarian Revolution.

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

A statue in Budapest's Liberty Square honors the former U.S. president's efforts to end the Cold War.

Central Europe's largest collection of mini-bottles is on display at this museum devoted to a bitter Hungarian liquor.

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

This Slovakian statue of an emerging sewer worker might just be a bronze peeping tom.

This Slovak bridge is known both for its connection to a national uprising and its UFO-shaped eatery.

Vienna's giant wonder wheel had a starring role in one of the greatest noir movies of all time.

A spherical "micro-nation" in the heart of Vienna.

Op-art architecture designed for happiness.

Baroque celebration of the end of the Great Plague of Vienna.

Vienna's diversity-themed traffic lights were inspired by the Eurovision Song Contest.

The Habsburgs' royal collections of art and wonders.

This legendary city has been a tourist attraction for centuries.

The engineering wonder and pleasure dome of a much-maligned emperor still holds undiscovered secrets.

These hut foundations are believed to be the residence of Romulus, founder of Rome.

An ancient Roman temple first dedicated to an emperor's wife is now a church.

An ancient Egyptian obelisk is now used to commemorate fallen Italian soldiers.

This ancient market is often referred to as the oldest shopping mall in the world.

A rare example of a medieval house in Rome adorned with a melancholic inscription.

A treasure trove of Renaissance-era funerary art in a Roman church built on top of Nero's grave.

Hidden beneath the famous St. Peter's Basilica is a veritable city of the dead that may hold the remains of St. Peter himself.

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