I believe it's not easy to build something massive and 'blocky' like a stronghold or a castle and yet you managed to give it enough detail to make is really interesting to explore.
I especially love the 6th pic (main pic included) where you look up to the castle. With sky in the background it would look amazingly real.
Ordinarily this would have blank grey wall syndrome with those big, sparingly-decorated walls, but you've come up with a great solution: mixing grey and bley! It adds a subtle variation that breaks up the monotony well. Great work!