It contains several large ventilator shafts as well. The brickwork is done to an incredibly good standard of detailing - you can see where the money went on the Jubilee Line extension.
I still haven't worked out which idiot (or colourblind?) Lambeth planner requested* that it should be clad in red brick to match the Edwardian buildings on Exton Street (?) rather than London stocks to match the buildings of Roupell Street/Cornwall Road.
I tried in vain to get that changed before they started construction however many years ago it was.
(* ironically, they only had advisory rights as the works were given planning consent by legislation rather than a planning application)