Remains of an abandoned coral city.

This historic building displays the remains of a victim of the devastating 14th-century plague.

It's a mystery why these remains were found with no traces of their bodies in sight.

One of the figures in this Celtic sculpture continues to puzzle archaeologists.

These morbid carvings remind churchgoers of the inevitability of death.

These mysterious Viking chess pieces spent centuries hidden on a remote Scottish island.

An unusual ode to the late Irish playwright, complete with a squiggly bust and coffin-shaped bench.

Where condemned pirates met their grisly end at the gallows on the River Thames.

This Viking gravestone carved in a rare runic style was dug up from a London churchyard.

The library houses an incredible collection of some of the world's most impressive books and manuscripts.

The "lost friend” is the most famous of the six moai statues that were removed from Easter Island.

More than a million titles fill the labyrinthine shelves of this prestigious private library.

A Roman spa buried deep beneath the City of London.

A monument to the thrice mayor of London who according to lore made his fortune by selling his rat-chasing cat.

Where Aleister Crowley attempted to seize the Hermetic Order of the Golden Dawn in a mask and a kilt.

This one has sailed five times as far as Sir Francis Drake's famous ship.

Following the trail of an old metro line, this scenic path is haunted by a creepy spriggan statue.

A collection dedicated to the treatment of disease, held in London's oldest hospital.

An existential riddle in the world's largest ancient castle.

One of the famous Czech artist's lesser-known Prague installations appears to be a glowing fetus affixed to a drainpipe.

This walkway is so narrow it needs its own light to stop pedestrian traffic jams.

Bullet holes in the church wall are a reminder of the violence that followed the assassination of a high-ranking Nazi officer.

A former squatter's paradise outside Prague.

Monument to a suicide protesting the Soviet invasion.