Batman: Arkham City DLC due Dec. 20

Last month, Warner Bros. Interactive Entertainment announced that Batman: Arkham City shipped 4.6 million copies in its first week on sale, which is more than twice that of its predecessor, Batman: Arkham Asylum.

Rocksteady Studios is planning to keep the momentum going with the announcement of a new downloadable content pack, which is set for release December 20.

The developer officially announced the new DLC via the Arkham City News Twitter account, revealing the new add-on will take the action outside of Arkham City and into Bruce Wayne's batcave.

"Brand new DLC coming December 20th with all new Batcave. Jokers carnival and the iceberg lounge also available to download the,!" the studio tweeted.

No other official details on the pack--including price--have so far been released, but judging by the studio's previous Robin and Nightwing DLC packs, the batcave may also be a challenge map. The other two maps--Joker's Carnival and The Iceberg Lounge--were originally offered as preorder incentives and as part of the collector's edition. Both maps require players to achieve the highest score possible by utilizing a combat gauge and surviving enemy attacks.

For more on the game, check out GameSpot's review of Batman: Arkham City.