Porthmadog, Wales, United Kingdom. It was formely a huge estuaria and made into a polder more than hundred years ago. It's called Traeth Mawr, which means big beach in Welsh. I love this view too and it's on my doorstep!
hmm... just looked it up on Google so now I can place where you are and saw a few more pics... how amazing! The next time I'm in England (my husband is British) I might just have to convince him to go for a visit out there... I'd like to see this for myself!