In December 1939, it was fully operational.[4] The complex consisted of twelve three-storey buildings above ground designed to look from the air like local housing,[5] and two floors of interlinked bunkers with two-foot thick walls below. Deeper in the subterranean levels of Maybach I, there were wells for drinking water and plumbing, air-filter systems for protection against gas attacks, and diesel engines to keep the system operational.[6] Later the site was further camouflaged by the use of netting.