Very good. You seem to have a little trouble with light source though. Or maybe just lazy? For instance the blocks just above the entrance on the right side look 3d and awesome but then the rim of the entrance looks flat on the outside. Especially the down part on the right side. The circle block above the entrance looks like the light is coming from the other way. The blocks on the left side look flat. The texture on the blocks looks really good. The texture lines on the ground make it look like a hill instead of a level ground and as such make the building look slightly skewed. So perspective is good, but could be better. The inside of the entrance looks like the light is coming from the right where as the outside of the tower it is coming from the left. I could be wrong about that though, maybe it's a reflective source. Overall I'd say you did a great job especially with this medium.