TThe Raft is one of four specialized, high security prisons maintained by S.H.I.E.L.D. along with The Big House, The Cube, and The Vault. The Raft was the place where only prisoners too dangerous for the other S.H.E.I.L.D. prisons. The Raft complex is actually deep underwater at the bottom of the ocean, with a garbage scow at the surface as cover.