The castle at Portencross dates to the 14th Century and is thought to have been used by the Scottish Kings as a halfway house between Dundonald and Rothsay. There is a story that Robert the Bruce stayed here.
It was used to house French prisoners of war in the early 18th century until the roof was destroyed during a storm in 1739, after which it became a ruin. The castle has undergone some restoration recently.
The Spanish Galleon
Local lore suggests that there is a wrecked Spanish Galleon somewhere beneath the waves not far from where the castle stands. The Galleon was one of the ships from the Armada of 1588 that had escaped by sailing through the North Sea and around the coast of Scotland, only to sink in bad weather just of the coast here. In one local story it was lured onto the coast by wreckers, who plundered the Spanish gold and hid it somewhere in the area
A cannon from such a ship was allegedly discovered in 1740 adding some evidence for the story, and Spanish coins have also been discovered. However, the location of the ship and its burden of riches is still to be discovered, and the coast is a popular diving location for would be treasure hunters.