Building 21 is a new area in DMZ mode but the mysterious laboratory has been a bit of a confusing mystery.

Call of Duty: Warzone 2.0 recently had some major updates for DMZ mode, including a new area called Building 21. But it hasn't been easy for all players to locate this mysterious building.

Building 21 is a clandestine biological laboratory that "will take players outside of Al Mazrah and into a hyper-dangerous new area of DMZ," according to patch notes. So where exactly is Building 21?

Where is Building 21 in Call of Duty: Warzone 2?

Building 21 will work similarly to The Lab in Escape From Tarkov, the survival game that DMZ mode appears to based on. This means that Call of Duty players will be able to select Building 21 instead of Al Mazrah from a level selector.

In order to access the new level, however, players will need to find the access card in Al Mazrah and successfully extract with it. Since Building 21 has the Chimera assault rifle and other high-tier loot, it's most definitely worth the effort.

Building 21 is currently not in the game, but players can gain access to it meanwhile by getting an access card. When Building 21 arrives, you'll be able to select it from the level selector.

How to find the Building 21 key in Al Mazrah

You'll have a chance to get the access key in a variety of ways. This includes SAM site drops, airplane supply drops, and the Commander Helo supply drop.

SAM sites are marked with a white icon on the map. Head to that area and clear out all of the AI enemies. Activate a console to initiate a countdown. You'll then have to defend the area against more incoming AI enemies. But once the site is secured, the missile battery will shoot down airplanes passing overhead, releasing a supply drop you can loot.

When the kick off timer hits 10 minutes during a match, you can also check out airplane supply drops. Airplanes drop three supply drops in its path, marked by an orange dollar symbol on the Tac-Map.

One of the most difficult ways to obtain the access key is from taking down the Commander Helo. Journey to the white skull icon on your map.

The last way to get the access key is by taking it off of an enemy team. If you can take it from them and successfully extract with it, you'll have access to Building 21.