The stately remains of Llywelyn the Great's mighty fortress.

Picturesque ruins once held off mighty armies.

This picturesque archeological site looks like it was pulled straight from a fantasy novel.

These haunting ruins belong to an ancient village that once had one hell of a view.

A magnificent, iconic stone tower in the Scottish Highlands.

Overlooking a Scottish loch, this beautifully crumbling castle once inspired a poem by William Wordsworth.

The ruins of this medieval castle in Northern Ireland have inspired artists from C.S. Lewis to Led Zeppelin.

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

These ruins witnessed the final gathering of the failed Jacobite Rebellion.

Remnants of the Roman empire's northern frontier nestled in suburban Glasgow.

This castle resides in a valley known for immense bloodshed during the Middle Ages.

These precariously placed ruins harken back to a 13th-century castle.

This ancient abbey now lies in majestic ruin behind a caravan park.

Also known as "Leicester's Folly," this almost cathedral was left unfinished and in ruins.

A deserted medieval village where bodies were once mutilated to prevent them rising from the dead.

The last two abbots of this monastery were both executed by Henry VIII.

Believed to be the former location of one of the earliest Viking assemblies in Europe.

The remains of a 13th-century stronghold built by the Welsh prince known as Llywelyn the Last.

Once considered one of the country's finest motte and bailey castles.

This tidal island, a sacred site in early English Christianity, was the target of a notable Viking invasion.

These ruins saw a second life as a cemetery.

The remains of one of Wales’ great medieval buildings, with a pub in the cellar.

Believed to be the capital of the the ancient kingdom of Dál Riata.

The bombed out remains of the old church were kept intact next to the new one, as a reminder of the futility of war.