"Baikonur spaceport. The assembling and testing hangar of carrier rocket Energia. Assembling of the first and second stages."
(Note: the decription refers to multiple photos. This one shows one of the high bays of MIK RN, where the second (core) stages were assembled.)
"The Energia Blasts Off", Mashinostroyeniye, 1990
Processing by The Energia-Buran Archive