A 2000-year-old Roman amphitheater lies just below Guildhall Yard.

The anatomical-pathological collection of a man who changed surgery.

A charming 17th-century alley is lined with secondhand bookstores and antiquarian shops.

A kaleidoscopic warehouse-maze of handmade neon signs.

"There's nothing there," and other lies the KGB told us.

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

A vista of the city and sea from atop the little-known viewing deck on an unassuming Columbus statue.

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.

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

These secluded and abandoned anti-aircraft defenses have become one the most scenic viewpoints in Barcelona.

Week-long block party becomes a competition for the best decorated street.

A beautifully eclectic mix of architectural styles.

Museum housed in underground tunnels that date back to Buenos Aires's earliest settlements.

A bright little alley in La Boca is a part of tango history.

Buenos Aires' city of the dead contains some very famous remains, including Eva Perón.

Xul Solar was an artist of alternate worlds, inventor of languages, and dreamer of utopias.

This historic, palatial theater is now one of the world’s most beautiful bookstores.

A monument to the thrice mayor of London who according to lore made his fortune by selling his rat-chasing cat.

This statue honors the thousands of Allied avians that served and died for France during World War I.

Those with a sharp eye can find the hidden image of a German Shepherd on the memorial's Mural Wall.

A mysterious shape catches the eye in this 16th-century painting.

Sculptor Antony Gormley used chaos theory and fractal growth to design his tallest creation.

A giant scrawl on the skyline of south London.

The unexpectedly beloved remnants of a controversial thermal power plant.