An important landmark in the history of algebraic logic.

This Irish museum in a historic 19th century market pays tribute to the glory of butter.

This hauntingly beautiful cemetery outside a medieval citadel is full of winding paths and ivy-covered graves.

One of the most controversial statues in Romania is an emperor with no clothes.

This memorial to the victims of the Romanian Revolution of 1989 is often compared to a potato on a skewer.

At less than four inches in height, this iconic fictional character is the smallest public statue in all of Moldova.

This funky former tobacco factory is one of the most striking examples of Madrid's cultural diversity.

This sweet-toothed bear searching for snacks has been a symbol of Madrid for decades.

For decades, Puerta del Sol has been illuminated by a giant, guitar-wielding bottle of sherry.

This lucky bronze frog was gifted to Madrid by a casino.

This macabre masterpiece of a mural is one of Francisco Goya's "Black Paintings."

Originally built to monitor fishing, this Victorian tower now educates visitors about the local salmon industry.

The comedy and tragedy of Oscar Wilde is preserved in a Dublin park, captured in a sculpture of colorful stone.

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

Dublin's most modern, visually spectacular bridge is modeled after Ireland's national emblem.

Experience what life was like in Ireland during the Viking and medieval ages.

The "Greatest Sewer" of ancient Rome is one of the oldest sewer systems in the world, and is still in use.

The only "Egyptian" pyramid in Europe and the legendary tomb of Remus.

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

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

An early 20th-century bullring converted into a modern shopping center.

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.

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.