Get on the Terrorist Mountain
Go to the Fenced off Breaching Game in front of the Terrorist Mountain, if you are a seal, to your right will be a Turret Window, with a turret inside. Go there, if your a terrorist, turn left when your at the breaching door. Do the Jump Anywhere(prone, run and jump) built in add-on, toward the front of the turret, if you did it right, you should be on the window ledge, press stand and then jump and you will pop up ontop of the mountain, usually you fall straight out of the window though, and it is very hard to do.

Spy on Seal's
There is a entrance to the Terrorist's Spawn without breaching, under the Antenna mountain, go in there, and you should see a box that is facing the opposite of the cage area, prone jump onto it, and then aim up or down and you can see outside.