Greenan Castle is a 16th-century ruined tower house, around 4 kilometres southwest of Ayr. Situated at the top of a sea cliff, it was originally a promontory fort converted into a motte-and-bailey in the 12th century. In the 15th century a tower house was built by the Lords of the Isles, which later passed into the hands of the Kennedy family.
The first known defensive structure on the site was a promontory fort, probably a fortified farmstead. Four concentric curved ditches, each around 3 metres wide, cut off the headland with the exception of a single causeway to provide access. It is not known how long this settlement was occupied, but the site was re-used in the twelfth century.
Beside the tower are traces of a walled courtyard and outbuildings, probably stables and a kitchen block, as the small tower has no kitchen within its walls.
The castle passed through various members of the clan before ending up in the hands of Thomas Kennedy, Earl of Cassillis in 1766. Around this time the residential use of the castle seems to have stopped; today the structure is a ruin.
References:The Walls of Constantinople are a series of defensive stone walls that have surrounded and protected the city of Constantinople (today Istanbul) since its founding as the new capital of the Roman Empire by Constantine the Great. With numerous additions and modifications during their history, they were the last great fortification system of antiquity, and one of the most complex and elaborate systems ever built. They were also the largest and strongest fortification in both the ancient and medieval world.
Initially built by Constantine the Great, the walls surrounded the new city on all sides, protecting it against attack from both sea and land. As the city grew, the famous double line of the Theodosian Walls was built in the 5th century. Although the other sections of the walls were less elaborate, they were, when well-manned, almost impregnable for any medieval besieger.