Watch for the turret at the bottom of the stairs. Or you could walk down the steps and try to take the CP opposite yours on the map, being careful not to outrun your allies. If you're up for a challenge, move through the city to the Keep (4), and take out the enemy soldiers hiding amongst the many pillars and ramps. There is simply no way to take this one by yourself. There's only one way to get to this command post, making it difficult to capture and easy to defend.Opposing units tend to hide behind it and wait until all your allies go away, then recapture it. Your enemy's starting command post, also enclosed in an outlying building.
Its capture is this level's secondary objective, meaning that the team that loses control of it will receive a larger drop in their reinforcement count than when losing a normal CP. It can be a pain to find people among all the pillars and tombs, so try not to let the enemy get this one.
It's really easy to capture from the catacombs, not so much from the other direction. It's inside a building that's detached from the main citadel, and it's really easy to defend.