This historic address is home to the beloved ball and is an almost totally empty building among the most expensive real estate in the world.

There must be a pun in this haystack somewhere...

Hear the quietest sound from across the dome.

Famously misunderstood wonder of the ancient world

In Florence's great Duomo, a 26 foot fresco honors a mercenary famous for attacking Florence.

Massive puppet-automaton machines created by French artist collective Machines de l’Ile.

This 1,300 year old monastery built atop a single rock was once only accessible depending on the whims of the tide.

Paris' linguistic guide to the international language of, yes, love.

France's most famous cemetery, with some of its most curious tombs.

This museum houses an imposing skeleton army comprised of creatures great and small.

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

A copy of the Statue of Liberty greets visitors to the birthplace of Auguste Bartholdi.

This modern French ossuary contains the jumbled bones of 130,000 WWI soldiers.

Site of one of World War I's most horrific scenes.

A fantastic castle rumored to be the birthplace of King Arthur.

A island reachable by a causeway at low tide is possibly one of the earliest Western European locations to be identified in text.

Sometimes an island, sometimes a rocky outcropping connected to the world by a tiny suspension bridge.

Climb inside an iron crystal magnified 165 billion times its normal size.

This spaceship-like Serbian monument reaches for the stars in celebration of the fallen fighters of fascism.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

Structure built from the skulls of vanquished foes.

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

Holy Grotto of Montserrat Monastery holds one of Europe's mysterious black Madonnas.