Georg Christian Unger ( 25 May 1743 -- 20 February 1799 ) was a German architect who was a pupil of the architect Carl von Gontard and served Frederick II of Prussia .
Georg Christian Unger ( 25 May 1743 -- 20 February 1799 ) was a German architect . He was a pupil of the architect Carl von Gontard and served for Frederick II of Prussia .