RobSpeer didn't design it so who did? Who built it? Many thanks... Rob.
The complex was built in two distinct phases, one part in 1936 and the other in 1943. The 1943 development was built by the Hochtief company as part of an extensive program of subterranean construction in Berlin begun in 1940. The accommodation for Hitler was in the newer section.
this is the website of the company who build a lot of things during the reich atlantikwall, viking etc ...
http://www.hochtief.com/hochtief_en/97.jhtml
fun
This is one of the last pictures taken of Adolf Hitler in his bunker in Berlin in 1945 as he shakes hands with Col. Gen. Ferdinand Schoerner, appointed commander in chief of the nonexistent Wehrmacht in Hitler's last will and testament. In the doorway stands Hitler's adjutant, Julius Schaub. Planning to commit suicide since he'd entered the bunker, the day after his wedding Hitler penned his last will and testament. Most of the rambling document tried to blame the war on "international politicians who either come from Jewish stock or [were] agents of Jewish interests."
The Remains of the Bunker
Sightseers walk amid the ruins of Hitler's bunker, sometimes referred to as Hitler's "tombstone," after a detachment of Soviet army engineers blew it up on Dec. 11, 1947. The ventilating tower of the shelter (a cylinder with a conical top) is at right. Stones from the shattered bunker, where Hitler and his mistress, Eva Braun, reportedly committed suicide, spattered the broken walls of the Reich Chancellery (background), and a few landed in the middle of the huge room that once was Hitler's office.