Battery Park is a location in New York City visited by JC Denton in Deus Ex. By the time of the events of the game a shanty town (with largely sheet metal buildings) has formed in the park, inhabited by a mix of junkies, Gray Death victims and those who has been forced into homelessness by other factors. According to an infected inhabitant, the police allow their presence in the park and that argument is backed up by the fact that after the NSF crisis in the area is resolved, they are allowed to return. At least one member of the Mole People occasionally spends time there.
Near the beginning of the game, the NSF use Battery Park as a small base of operations for naval transport. By the time the player arrives, the NSF have barricaded themselves within Castle Clinton. While the main courtyard in the castle is heavily guarded, there is also a backdoor entrance to the base. In addition, the NSF also raid the nearby subway station, taking hostages and threatening to destroy the platform with TNT.
Battery park is encountered once more, where JC Denton is captured (if he wasn't already). After this, the subway entrance to Battery Park is closed for good.