Spain's unique Mosque-Cathedral has been a place of worship for both Muslims and Christians throughout its history.

Touching this little fossil embedded in the wall of a grand mosque-cathedral may make your wishes come true.

In one of the smallest countries in the world stands an original Salvador Dalí sculpture.

The 2,000-year-old Roman columns are hidden within Barcelona's Gothic Quarter.

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

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

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

These enormous, stern-faced statues greet visitors with lanterns, and sometimes costumes.

Site of the first radio and telephone broadcasting companies in Copenhagen.

Traditional Danish spot where the schnapps are flowing and the smørrebrød is loaded.

The old observatory in Copenhagen has a spiral corridor used as a racetrack.

Once a meeting point for great thinkers, and the midpoint of the country.

Climb to the top of its spiral spire for spectacular views of Copenhagen.

Hamburg's first legal sex work is relegated to a gated street that still does not allow pedestrian women.

Hamburgers are intensely proud of their tunnel beneath the river.

Once the tallest building in the world, this abandoned church is now a monument to the destruction of WWII.

One of the oldest wine cellars in Germany is now a restaurant beneath Bremen's town hall.

Designed to resemble foreign architecture, this mosque-looking structure was used to pump water to a royal fountain.

The "Prussian Versailles" that is as glorious today as when it was built.

This World War II bunker now survives as a documentation of the Nazi regime and war crimes.

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

Super-heavy Nazi architectural experiment.

An imperial church bombed to ruins during WWII now stands as a jagged memorial.

At one of Berlin’s oldest churches, visitors can place mosaic tiles to help restore a medieval mural.