A gorge full of caverns where early humans lived alongside cave hyenas, giant mammoths and wooly rhinoceroses.

The world's first military tank was designed in this English city amid the stalemate of WWI trench warfare.

From here, the loch appears to take the shape of mainland Scotland.

A open air theatre built on a cliff by an eccentric British woman.

The location of this historic castle was inspired by a donkey.

A well preserved remnant of the English Civil War.

A glacial pothole was once a hideout for a notorious Scottish outlaw.

The undercroft is a spectacular example of medieval Cistercian architecture.

In this medieval fish bowl, the carp weren't pets.

A restaurant devoted to "trouser grip" wrestling, an ancient form of Viking wrestling that is Iceland's national sport.

This valley of hot springs and boiling mud pots is home to the record-holding "Geysir," which originated the English word.

Medicinal spa created with the discharge from a geothermal energy plant.

This eye-popping Icelandic crater lake is surrounded by red volcanic rock.

In the U.K., a historic workhouse shines a light on the early, harsh treatment of the poor.

Exquisite carvings of leaves, Green Men, and the occasional dragon adorn a medieval chapter house.

The picturesque birthplace of Icelandic democracy is drenched in the blood of its brutal past.

Once a palace for the Archbishop of York, these 15th-century ruins now serve as a haunt for history buffs.

One of the earliest large-scale "hyper" roofs in the U.K. is now a derelict roadside attraction.

This English medieval castle is where King John died of dysentery.

Lord Byron's embalmed body lies within this medieval church.

The largest oak in England is said to have been the hideout of Robin Hood and his Merry Men.

The oldest of the three remaining bridges in England with buildings on top of them.

This memorial pays homage to the Royal Air Force squadron that breached two important dams during World War II.

Legend says this demonic carving inside a medieval cathedral was one of Satan's minions.