Picturesque ruins once held off mighty armies.

America's most famous museum of medical oddities is home to the remains of Albert Einstein's brain.

Huge masonic hall in Philadelphia with lavishly themed rooms.

A layered tribute to the work of mosaicist Isaiah Zagar.

A Pythagorean funhouse that tries, successfully, to prove that math is the coolest thing ever.

The Sun King's military models, saved from the Louvre.

Go surfing on this urban wave, "hacked" by local surfers.

Daily jousts and dancing barrel makers in Munich's mechanical clock.

Gaze upon chocolate sculptures depicting everything from chariot races to Gaudí's famous church at this shrine to sweets.

On the Spree bank, discover one of the last reminders of a symbolic wall that divided, and was torn down by the people.

Cold war icon and onetime "hole" in the iron curtain.

Christ's blood allegedly preserved in a Belgian town.

This 17th-century street hidden beneath Edinburgh was once a breeding ground for the black death.

London's creepiest cemetery was once the site of dueling magicians and mobs of stake-carrying vampire hunters.

The curios of pharmacist and collector Henry Wellcome.

Catacombs turned marketplace.

Scattered throughout London are ancient remnants of the city's former bounding wall.

Hear the quietest sound from across the dome.

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

A cluttered and astounding collection of antiquities and curiosities.

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

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

This bridge was constructed from the rubble of the infamous Bastille.

Remains of Roman amphitheater hidden in a sleepy quarter of Paris.