This a cross section dating from 2002, showing all three levels of the Gartenhaus.  The gallery is located on the ground floor, reached by 4 steps.  The ceiling height is given as 3.40 m, the windows as 2.10m.

 

This plan from 2002 gives an idea of the gallery floor space.  It measures approximately 50.5 m2, with a 9.12m front wall.  This plan also shows the position of the four windows.  A more detailed plan, with the back and side wall measurements will be available soon!