Chris G.
Google
These are the remains of Roman baths. Now they are rectangular walled areas with tunnels and channels leading to the sea. They fill up at high tide and are a great place to do some snorkel as there are usually lots of fish about. The water gets very warm here being enclosed. The rocks are slippery so take care. If approaching from the sea there’s a cool rock arch tunnel you can swim through. There are steps down from the promenade too.