Here are a "few" things I want to say:
Spawnrooms:
Textures could be aligned better. You should also smooth (smoothinggroups) these round corners.
Try to use a bit of the darker metalbeams to give more contrast.
The Visualisers' texture needs to be bigger and centered.
BLU Side:
The Cave Underneath the room is a bit out of place.
Because of the side room, it feels more open than the RED Spawn.
Also, the projected picture is floating in mid air. This doesn't seem right at all...
RED Side:
It's weird that this side doesn't show as much rockwalls. RED is supposed to have more natural things than BLU.
The Rockets in the backroom are strangely placed. They are pointing directly towards the BLU Spawn. The Boardthing behind them is pointless imo.
Paylaud Track:
Carts are starting from nowhere. Did somebody carry these bloody things to the track?
The tracks at the cross section are z fighting. The piece of wood that is going through the concrete is pointless.
At the middle upper part there is a wood beam going only half way through the ground.
At the end the holograms are beeing summoned into existance by black magic.
Other:
The bottom area underneath the tracks is partially badly lit. The displacements also seem to be of low power. Or they are just too big, as they are going through every building.
The bridge in the middle is shaped in a weird way. There needs to be a reason for that. A single lamp on the bottom is devinately not enough. (I would have used a few light bulb models and connected them with cabels. Yes, you can use cabels for other things than telephone poles.)
The more important (walkable) roofs should have something that shows "YOU CAN STAND ON ME". Try making the walkable roofs brighter than the not walkable ones.
I saw you using roof drainage above another roof. Perhaps there are some better places for such detail?
Also, clipping. Lots and lots of clipping.
For the end I just want to point some things out using a few screenshots: