Historic medieval fortified city in southwest France.

This massive blockhead sculpture hides an entire library.

Monument to a suicide protesting the Soviet invasion.

This Prague museum collects brutalist relics and memories from the country's former Soviet rule.

Increasingly decayed figures stand as a powerful reminder of the human costs of Czech Communism.

Macabre astrological automaton clock dating to the late 1400s.

Cat art as far as the eye can see.

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

A little sculpture with a large wardrobe.

A church of bones, decorated with 40,000 human skeletons.

Museum dedicated to the terror regimes of Hungary.

A 1,215-foot tunnel transports pedestrians beneath the River Thames.

Allowing humans and fish alike to migrate from freshwater to saltwater and back again.

Hear the quietest sound from across the dome.

This South London cemetery holds the remains of more than 15,000 people.

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

The most loyal of little dogs, or a Victorian era publicity stunt?

Protecting the dead from opportunistic body snatchers.