A vast Communist-era exhibition space in the Bulgarian capital.

A striking symbol of the Bulgarian capital.

Historic medieval fortified city in southwest France.

One of a series of no-purpose kinetic artworks by Swiss sculptor Jean Tinguely.

The bears of Bern have been a city highlight for over 500 years.

CERN's beautiful, bending sculpture is a tribute to the spread of knowledge.

The world's largest second-hand graces a clock surrounded by constantly changing flower beds. 

The highest peak in the United Kingdom has a history of physics, specters, and a pilgrimage of strange objects.

A tiny church on a man-made island in the Adriatic.

These historic defenses ensured the city within would survive hundreds of years of occupations, sieges, and invasions.

The possible imprisonment of Vlad the Impaler here earned the medieval castle its nickname, "Dracula's Castle."

Five candy-colored villages on the Italian Riviera.

The largest and best-preserved Roman amphitheater in Africa was designed to seat 35,000 people.

The largest salt lake in the Sahara is mysteriously alluring.

The original film set of Luke Skywalker's Tatooine home from the 'Star Wars' trilogy.

A 15th-century granary that played the role of futuristic slave quarters in the world of 'Star Wars.'

The original movie set for the home of 'Star Wars' hero Luke Skywalker.

A tribute to the man who lit himself on fire and ushered in the Tunisian Revolution.

Giant topiary dog once played a role in a terrorist bomb plot.

Two towns are linked by an engineering marvel masquerading as a boring suspension bridge.

This weird, elephant-shaped rock also hosts two ancient tombs.

This grand hydraulic installation has provided water for townspeople since the Middle Ages.

Founded in 670, this ancient mosque is an architectural time portal.

A man's head is enshrined beneath a statue near the first building constructed for the modern Olympic Games.