It is perfectly symmetrical and has a severe lack of diverse scenery & coloration. The middle section doesn't look free-flowing (including the high top two boulders, which look rather vestigial). The curving bottom corner tunnel is an interesting idea.
I especially hate the symmetry since there is no single light source distinguishable throughout the map. The only shades you changed throughout the whole bland blue were in the middle areas, the base colors, and the main hill on the left side (being a bit brighter than its counterpart). I should not be able to pick out all of your coloring differences from the overview.
Slice it in half, make a differing other side, do something with the center so that it's not like a diagonal wall as it pretty much is at the moment, and use MUCH more scenery and more than just blue shades. The boulder structure reminds me of ctf_B2b, kind of; making the middle a bridge with a hole in it or something would be pretty neat. It needs a LOT more scenery-based elements like that; the prevailing blue theme kills its potential for scenery.