This Roman amphitheater is said to be King Arthur's legendary Round Table.

The enormous earthwork sculpture honors the ponies that lived and worked in the old colliery.

A hidden tunnel leads to an abandoned slate quarry that's now a secret swimming spot guarded by cliffs.

A little-known castle set in a nature reserve.

A holy well believed to have healing powers.

A breathtaking flower tunnel bursts with beautiful golden blossoms.

This 6th-century church honors St. Tudno, the patron saint of Llandudno.

A former fisherman's hut deemed too small for habitation is now a delightful tourist draw.

After years of slow decline, a derelict Gothic castle is now being restored to life.

The oldest continual pilgrimage site in Britain was supposedly created by a gruesome beheading.

At the United Kingdom's only residential library you can sleep among the books.

The U.K.'s first underground railway line is now a lively thoroughfare for runners and cyclists.

This stack of stones honors a murdered 18th-century woman.

Many of Edinburgh's more unsavory characters spent their final days behind this door while awaiting their executions.

These steps offer a breathtaking view of one of Europe's most besieged fortresses.

The remnants of a facade from a 19th-century market stall emporium.

Macbeth's infamous "Great Birnam Wood."

One of the most spectacular 18th-century bridges in Scotland.

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

A sacred site for Native Americans surveyed by George Washington and owned by both King George III and Thomas Jefferson.

Bubbling up from deep underground is the warm crystal clear water that fills the Warm Springs Pools, America's oldest spa.

A 300-yard long natural tunnel runs through a ridge deep in the Appalachian Mountains.

This maze-like slot canyon is a unique gem within an already fascinating geological area.

This famous church is adorned by a mural commemorating the independence of Vatican City.