This is gorgeous, the rolling hills, the sand and sea, the beautiful sky and the hint of somewhere else on the horizon. The picture has a very deep 3D feeling to it. The EXIF says you shot at f4.0 which I wouldn't have expected to give such a feeling of depth but then maybe the 4.5 wide angle contributes?
I haven't visited this castle and yet we used to go to Swansea and The Mumbles quite often. Now seeing your photo I wish I had been there. It looks great.
My sister in law lives in Swansea, but I haven't been there for years.