Pretty nice map.
I think you should use some texture blending on the ground outside the map like you did inside it, as looking out at a same-texture field looks pretty bad. Also, there's some spots where you can't fall out into the water because of invisible walls, but some places (like the circular holes in the wall) that you can jump out and die.
Even though there are trees around, the map seems a bit dead. The place it too ruined to be so perfectly clear of grass and shrubs.