This fortress looks very good, especially walls, as i see (maybe i made a mistake) you inspired by the wall of a set of 79012,
But you made them much higher and, you have made these walls more natural, severer in appearance,
And tower in original lego set is awful, your towers look much better, and the gates, I loved the leaves on them.
I think if this was a set of modular, it would be even more beautiful, just imagine, two of these sets, would make a great(really great) elven fortress.
And of course the ballista looks very original.