Since the main entrance is collapsed, the tunnel is entered through a door built into a wall on the side. There are several irradiated pools outside of the gate as well as an intact Army truck loaded with Aqua Pura crates.
The interior consists of a short stretch of intact tunnel with the thrashed remains of the Enclave's former occupation scattered all throughout (barricades, turret, supply crates, etc). Now the premises has been claimed by Brotherhood of Steel knights and scribes. One small service corridor on the southwest end connects the tunnel with the Capital Wasteland, while another one in the northeast corner heads toward the Satellite Relay Station.
Seven sets of Enclave power armor can be found inside of the tunnel on piled bodies of deceased Enclave soldiers, in a bus stop on the east side of the main chamber, as well as lying among rocks along the west wall.
In addition several containers filled with random, valuable loot (a first aid box, 2 grenade boxes, 2 Enclave crates, and an unlocked safe) are also spread throughout the Brotherhoods staging area for the Battle of Rockland.
Finally, a room just off the entrance hallway holds five ammunition boxes.
- Before the completion of Death From Above's final objective, the Brotherhood of Steel seemingly abandons the tunnel, leaving all of the equipment and technology inside it.
- The tunnel cannot be accessed before Death From Above except from by the use of console commands.
- When traveling through the tunnel while fighting the Enclave, the Lone Wanderer will go off the main map.
- There is almost always a wandering hostile creature outside the gates near the irradiated pool and Army truck (often deathclaws or albino radscorpions at higher levels). This is not normally a hazard, as if the Lone Wanderer is on the way to complete Death From Above, nearby Brotherhood of Steel members will help the player character.
- Once inside the tunnel itself, it has its own world map.
- The Enclave soldiers' bodies never disappear, so they can be used for storage.
- It is possible to bypass the main gate through the path on the right side; however, the door is locked.
The Rockland car tunnel appears only in the Fallout 3 add-on Broken Steel.