Cube

The Cube is a secret S.H.I.E.L.D. facility at a classified location.

History
Skye tells Coulson that the Cube had been retaken during the S.H.I.E.L.D. Civil War and that all HYDRA agents were flushed out, making it the fourth secure S.H.I.E.L.D. facility known to Coulson's Team.