Dr. Schabb's Research Laboratory is the location of some of Doctor Schabbs the earliest attempts for Operation Eisenfaust. It appears in the SNES & Jaguar versions of Wolfenstein 3D, the Original Encounter/2nd Encounter in the Mac Family/3DO versions of the game.
The location of the secret research facility is unclear it could be at Castle Erlangen or Castle Hollehammer. It was the location where William Joseph B.J. Blazkowicz had his original encounter with Doctor Schabbs, but didn't finally defeat him until later on in the series.