The following is based on developer test content cut from Fallout 3 and has not been confirmed by canon sources.
DLCPittTestPurkey (named Mango power! on the local map) is a test cell in The Pitt that can only be accessed by using console commands. The console commands to enter these rooms are COC <cell name>, as it can only be accessed by console commands it must also be exited this way (i.e. COC DLC01SteelMill01).