You get sent there in the mission Wildlife Preservation
Upon entering the Specimen Maintenance, Mordecai tells you that Bloodwing should be in one of these cells and not to worry about the other ones, they can't get to you yet. Mordecai wants you to just get Bloodwing and you'll have what you need to upgrade Claptrap and get through that Death Wall. Follow the corridor to the last room and through the door that's aptly labeled "Domesticated, Extremely Dangerous - Bloodwing." Enter Bloodwing's Enclosure when you are ready, but note that it is a trap. Once inside you'll find that Bloodwing is not there; instead, Handsome Jack then comes on the communications net and taunts you. As you leave the empty Bloodwing cell, you soon realize that all the other holding cells have been opened. You'll now have to fight your way back out.
The Loot Box 'Glitch'
Before entering Bloodwing's enclosure, immediately before the holding cell and just the the right of it, is a room with a variety of loot boxes. On the right side of the room are four cardboard boxes sitting on the floor. Of those four boxes, three will have loot midgets. Many people have returned to this area for the express purpose of farming those three loot midgets.