Madrid's romantically ornate crystal palace has been offering shelter to plants and art for over a century.

This small 16th-century church in Athens is almost entirely surrounded by a modern building.

Where commuters walk through remnants of an ancient Greek necropolis.

Legend says this sacred tree was a gift from goddess Athena.

Heralded as the world's first theater, these ruins are often overlooked as they reside in the shadows of the Acropolis.

The Cycladic architecture makes this Athens neighborhood feel like an island paradise hidden in the shadow of the Acropolis.

An ancient octagonal weather station named for the eight Greek gods of wind.

The railway carts travelers to central Athens's highest peak, which offers stunning vistas of the city.

This ancient Greek place of assembly and marketplace is being revealed layer by layer below the modern Athens cityscape.

A 2,000-year-old computer demonstrates remarkable engineering and astronomical precision.

A beautifully eclectic mix of architectural styles.

An Orthodox church built by the Royal Family for the Russian community exiled to the French Riviera.

A striking symbol of the Bulgarian capital.

Monument to a suicide protesting the Soviet invasion.

This automated sculpture of two men peeing will spell out text messages with their micturition.

A bust of Franz Kafka spins in pieces, reflecting the writer's inner torment.

Around 100,000 bodies are buried below the medieval headstones, many of which mark graves with multiple bodies stacked up to 12 deep.

Macabre astrological automaton clock dating to the late 1400s.

Eighty million natural history specimens call this gargantuan museum home.

The popularity of Sherlock Holmes led to the creation of his fictional address, turning the orderly London street numbers askew.

Kings Cross Station pays tribute to its role in Britain's best-selling book series.

An open-air "garden" of mural art that changes weekly.

This home designed for chocolate magnate Antoni Amatller is an exquisite treasure-box of Catalan Modernism.

This former Baroque palace on the historic Calle Montcada is a rare architectural gem and was once the meeting place of an aristocratic scholarly society.