Have you no information at all? There's some writing which has been cropped off, do you have that?
I'm 99.9999% certain that's not a British Castle - we didn't have castles here until after the Normans came and those aren't the right sort of windows. On top of that, I'm pretty sure I'd recognise a castle of that size if it was here! And it's too hilly for the Netherlands.
My instinct says Central Europe, Hungary, Eastern Germany, Slovakia, Ukraine... but that's a large area which has so many castles you trip over them everywhere. Plus Southern France and Spain have a few castles with similar architecture.
It's clearly a castle/battlement protecting a town as there's a covered walkway of the sort found only in towns - they didn't build walkways like that just for soldiers.
So, any more clues? Why are you looking for this anyway?