Portencross Castle is a scheduled monument of national importance. It was built in the mid 1300s by the Boyd family after Robert the Bruce gave them the surrounding lands of Arnele in recognition of their support during the war of independence.

They chose this site as it allowed them to defend sea routes to the islands of the Firth of Clyde and beyond.

The family enlarged the castle later in the 1300s and early 1400s into the distinctive L-shape we see today. The original great hall and cellar are still in tact.

King Robert II used it during the period when the Stewart dynasty was being established (1371 – 1390) and the old harbour was an important ferry port giving access to Rothesay Castle and the royal deer forest on Little Cumbrae.

The bodies of Scottish kings were taken by sea from Portencross to their final resting place on the island of Iona.