A musical instrument played by the sea.

A chain of 16 wondrous lakes formed as a result of the gradual dissolution of soluble layers of bedrock.

An unusual round church in London with a Templar past.

An easily overlooked stretch of ornate window fronts and gaslight lamps that could be right from the pages of Dickens.

The yawning maw of this pagan visage is said to bite off the hands of liars.

A Nesting Doll of Churches.

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

The martyr's wax-enhanced skeletal remains lie preserved in a glass case in the Santa Maria della Vittoria in Rome.

One of the oldest medical collections in Europe focusing on rare surgical instruments.

This massive library holds what was once the largest book collection in the world.

A mechanized clock where a man fights off a dragon, crab, and rooster.

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

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

Notorious artist squat renovated into legal studios.

The very center of Paris is surrounded by a bevy of strange good luck rituals.

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.

Walk upon the mementos of the dead in this Parisian courtyard paved with medieval tombstones.

Located in the thermoelectric factory that once powered the entire city, this Portuguese museum is shockingly fascinating.

Elaborately carved to showcase the glorious wealth that the age of exploration brought to the Portuguese empire.

This Industrial Age architectural and engineering gem helps visitors and residents alike traverse Lisbon, “The City of Seven Hills.”

A king's pet, a pope's gift, an artist's inspiration, and a tragic shipwreck.

Legacy of the earthquake that nearly wiped Lisbon off the face of the Earth.

Over two centuries old and counting, Madrid's massive botanical garden contains one of Europe's only desert environments.