Now that you are in the city, the game will start to ramp up in its difficulty. If you want, as soon as you enter the streets, there will be a Rhino alien on top of a building that you can shoot to bring him down to you. The Rhinos are the toughest enemies in the game and you will get $1000 for killing it. In this section of the game, you will only need to destroy three different hives before reaching the barrier, but they are more difficult as they take longer to destroy and the aliens that attack are more varied.
Now you will face the regular aliens and Scorpions, as well as Seekers, Hunters, and Rhinos. Seekers have red bubbles on them and will explode when they get close to you. Hunters have plated heads and resist being hit from the front, and Rhinos are plated all over and are bullet sponges that can run darn fast. As you start drilling and taking down hives, enemies will begin to exit meteors that fall from the sky. These are large red crystals that basically look like markers from Dead Space.
Dealing with hives is the same drill (pardon the pun) as the previous section, but when you reach the barrier, things get a little more hectic. The barrier is between two buildings on a large wide open street and leaves a lot of room for aliens to attack and plenty of areas for scorpions to attack the chopper from. Always focus on the scorpions as much as you can to keep the helicopter attacking the barrier using turrets and sentries if possible.
There will be a ton of scorpions and they will leave their acid puddles everywhere and if you dawdle in them for too long, they can eat through your health and armor in no time. Also try to give the helicopter as much help as you can attacking the barrier, as this battle can go on for a real long time if not. Once you get the barrier down close to being destroyed, Rhinos will appear and can be rather tough to deal with. Have everyone in the squad focus on them until they are down and then focus back on the other aliens. Once the barrier is finally down, grab the drill and head through the alley to face another Rhino and continue to the next area, the Cabin.