This giant geoglyph of mysterious origins is now the site of neo-pagan rituals.

Now isolated, this church was once the center of a bustling village that succumbed to the Black Death.

Ancient Egyptian wigs, South American feather headdresses, a bounty of anthropological artifacts in Oxford.

One of Europe's oldest libraries.

This haunting stone chasm is a hotbed of mossy rock and English legend.

This beautiful "lagoon" is actually a toxic soup filled with cars, carcasses, and trash. When warnings couldn't stop people from going for a dip, the town dyed it black.

One of the largest sculpture collections in the U.K. features history's greats, from Bob Dylan to Galileo, in bronze.

Fantastically decorated underground chambers built in the 1760s.

Besieged by war, this castle ruin has crumbled into a peaceful picnic spot.

Created hundreds of years ago, the magical follies and landscapes at this park were almost lost to time before being restored.

A 200-year-old prison that now houses a peculiar crime museum.

Below a historic English market town lies a secret underground city complete with kitchens, laundries, storerooms, and an underground lake.

400-year-old garden, restored to beauty.

Mysteriously stacked storefront paths give this medieval British town an iconic style like none other.

Famously misunderstood wonder of the ancient world

The hidden "ballroom" under a mansion lake was built by a criminal who ate a cyanide pill during his trial.

The sign at the garden gate reads: "These Plants Can Kill."

Ireland's only German military cemetery holds the remains of a spy who was moved there under the cover of darkness.

A retired military stronghold on the rolling green coast of Donegal.

An ancient holy well said to be used by the patron saint of sailors and travelers, lost in the boggy west of Valentia Island.

An Irish town has built a statue to a silent film actor simply thanks to the holidays he once spent there.

An important pilgrimage site for pagans and early Christians, named for a Celtic goddess-turned-saint.

The largest portal tomb in Europe has a capstone weighing around 150 tons.

Ancient Bronze Age rampart that was used into the middle ages.