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

The ruins of an 11th-century Norman castle with a rare, perfectly circular shape.

This remote castle was built to be a wealthy businessman's palace of vice but is now simply a historic vacation cottage.

Spanish architects used seized Muslim gravestones to rebuild parts of the fortress.

An Iron Age fort on the edge of a seaside cliff offers a glimpse into an ancient, mystical world.

Not far from Madrid, a set of perfectly preserved trenches date back to the Spanish Civil War.

Among the oldest structures in Madrid, these Moorish walls once guarded the medieval city of Mayrit.

The city walls of Salé lead to the ruins of this seaside "bastion of tears."

The history of this Moorish castle includes royals, a Mexican-Spanish association, and several attempts at lodging.

A stunning medieval castle owned and restored by the famed actor Jeremy Irons.

This remote location of this Moorish stronghold means it doesn’t attract many tourists—and that it still has the aura of fear and bravery of the 1300s.

An eerie former warehouse turned cistern turned movie set.

This abandoned fortress still stands guard over the Guadiana River despite a history of warfare.

The largest medieval water tank on the Iberian Peninsula is preserved beneath the Cáceres Museum.

These ramparts, once lined with towers, were constructed in defense of Beaune.

A 16th-century artillery fort built to protect England against European invasion.

In the foothills of the lesser Caucasus, a centuries-old fortress still stands.

This hilltop ruin is of the hundreds of stone columns built in tribute to the first German chancellor.

This monument commemorates the soldiers who fought for 16 hours straight to penetrate this concrete fort.

This medieval settlement was abandoned after a series of landslides. What remained was largely destroyed during a mock battle for a WWII film reel.

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

This castle once belonged to one of the most prominent families of medieval Carrickfergus.

In the Scottish Highlands, this 13th-century castle ruin is hidden at the end of a farm track.

This network of tunnels housed an entire village for years, and even had a hall for screening movies.