As one of the only remaining symbols of the 1958 Brussels World Fair, this extraordinary structure, conceptualized by late engineer André Waterkeyn, represents an iron crystal magnified 165 billion times. It features nine spheres interconnected by 20 tubes. While three spheres contain either permanent or temporary exhibitions from around the world, it's the highest, at 92 meters (300 feet), that offers a spectacular panoramic view of the city.
Inaugurated in 2008 with the inconspicuous job of housing offices (official name, Office Center 1000), this remarkable building features more than 4,000 tiles of enameled glass, all pieced together like a puzzle.
The quirky design represents an antique 1,000 litu banknote, which bemuses by day and enchants by night -- the building is lit by an impressive display of primary colors.
Casa Mila, Barcelona —
Widely known as La Pedrera (The Quarry), this iconic building recently celebrated its centennial year. Renowned Catalan architect Antoni Gaudi designed it for a wealthy couple, complete with innovative features of the time including private elevators, staircases and an underground parking garage.
After years of neglect, Casa Mila was restored to its original glory in the late 1990s and today features a one-of-a-kind terrace and exhibition center created by the current owners, the Caixa Catalunya Foundation.
Castel Meur, Brittany, France —
The tiny Brittany town of Plougrescant's claim to fame is a puzzling little house situated between two granite rocks by the sea.
The residence was built in 1861 with a specific goal in mind -- to ward off the destructive heavy winds and storms the area is often troubled by.
After a postcard of the property created to boost local tourism caused such a stir with tourists that the private residence suffered damage, visitors can now only admire its unique form from a distance.
Dali Theatre-Museum, Figueres, Spain —
Built in 1974 on the site of the town's former theater, this inventive building holds the world's largest collection of Salvador Dali artwork.
Those not familiar with the surrealist artist's work might think that the large egg sculptures perched atop a dome and surrounding brick "castle" might just be a gimmick. Once inside, however, you realize the flamboyant façade pales in comparison to the wacky curiosities awaiting visitors.
More than 20 years after Dali's death, Figueres -- the town where he was born and later died -- continues to honor the eccentric master with a crypt containing his grave in the center of the museum.