First, the attackers start in a train car. When you leave the car you are in a city street. As you get closer to the building you are supposed to go to, there is a small alleyway to one side.
Right outside the entrance is an automatic machine gun. This causes quite a few problems if you want to survive long inside the building. Inside is pretty small. It is a small room that has an upper pathway around the room. And a hall that goes to the objective. The door to the room that you have to get in to destroy the receiver is locked shut and the only way to open it is hit a button in an adjacent room. Be very careful when hitting the button. If it is accidentally shot before you hit it, the door stays permanently locked and you lose.