A layered tribute to the work of mosaicist Isaiah Zagar.

Downtown Minneapolis mixed art and function by turning some of their sewer covers into works of art.

When flour explodes, it's not a pretty sight.

A Jenga-style cylindrical tower of books that appears to go on forever.

This tipsy office building in downtown Prague was originally called “Fred and Ginger.”

A turn of the century building boasting some of the most beautiful art nouveau architecture in Prague.

The slender brass strip in Prague's Old Town Square was used to tell time from 1652 to 1918.

An existential riddle in the world's largest ancient castle.

A surreal statue honoring Prague's favorite literary son.

A brush maker used his factory to protect blind Jews from the Gestapo.

A narrow passage next to a cafe leads to a courtyard exploding with murals, tags, and paste-ups.

Beneath the impressive baroque cathedral that rises from the center of Berlin lies the largest collection of Prussian royals in the world.

This life-size replica of the Statue of Liberty's flame is also a tribute to Princess Diana by default.

Noirish green neon marks the location of one of the oldest private detective agencies in France.

A 16th-century fountain marks the site of a lost medieval cemetery once filled with mass graves.

An unusual number plate signifies the building's saucy past.

Natural history museum celebrating biodiversity with a parade of taxidermy animals.

Remains of Roman amphitheater hidden in a sleepy quarter of Paris.

Twelve grave-faced marble angels guard the emperor's tomb at Les Invalides.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

This modest marker near Notre Dame identifies the very center of Paris.

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

A series of abstract, silly sculptures represent the works of a great modern classical composer.

This mouldering abandoned mental hospital was once a center for progressive healing.