An ancient ossuary in Rouen.

The perfectly preserved underground rooms where Churchill plotted the war against Germany.

Eighty million natural history specimens call this gargantuan museum home.

This shop and gallery is a modern-day cabinet of curiosities, unassumingly positioned along an urban thoroughfare.

Tables of secondhand books fill the inner courtyard of this 17th-century stock exchange.

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

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

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

The longest staircase lock in Britain.

A fantastical 13th-century fortification sandwiched by a modern hotel in central Brussels.

This Greek temple, open only an hour a day, was the site of a war of tastes between an architect and an artist.

Brussels' favorite peeing boy has a sister.

An Italian crevasse filled with abandoned buildings gives visitors a look at the world without humans.

Quite possibly the oldest love poem known to humankind.

This column celebrates Rome's victory over the Goths, and may be the oldest Roman monument in Istanbul.

No one is sure if the world's fourth-largest diamond had been found in a rubbish heap or was pawned by Napoleon's mom.

A fountain standing as a testament to a doomed alliance.

A tiny park in the middle of some big power politics.

A section of the long chain that blocked enemy ships from entering Constantinople.

Ancient serpentine sacrifice holder that has stood the test of time.

A gorgeous, Gaudí-esque stairway constructed in the city of Istanbul by a prominent Jewish family.

The most metal church of all time was built in record time because of an international, pious pissing contest.

Legend says if you stick your thumb in the hole and it gets wet, your wish will be granted.

1513 Turkish world map, full of European state secrets and snarky commentary.