I'm updating a trip plan I added last year. The beach in the picture is Portcurno Beach, viewed from The Minack Theatre. The sea is turqoise all year round and it feels like your in The Med with clear water, golden sand beaches and rugged coastline.
The Minack Theatre is the most amazing place I've ever been too. It takes your breath way. It was built by a lady called Rowena Cade who dedicated her whole life to making it what it is today. Even carrying buliding materials up from the beach below, she is a true inspiration. The Minack can only be reached by car as it's quite remote.
The castle is Pendennis Castle, in Falmouth, built by Henry VIII to combat the Spanish Armada in 1571 (ish)