Castle

I always go to the beach and I did when I was little and I remember a type of building on the beach opposite from the beach terrace cafe. I always thought it was castle ruins, it was made of big stones and it looked like it had been knocked down years ago. I used to play on it when I was little and then one day it was gone, it had been taken away, it was probably unsafe because it looked very old. I've tryed to find out about it but there is nothing on the internet about it. But on the old Google Earth you can see it but not on the street view. I wish I knew what it was and the history of it. If anyone knows anything about it please can you tell me by writting it as a memory.