Thun Military Training Area, by Paulus Roetter, 1834, near Thun, Switzerland.  There's similar artwork out there (such as Das Eidsgenössische Lager bey Thun von 1826, by J.J. Oesch) which means that this one has been occasionally misattributed to other artists.  Also, note that the cover photo of the book Thun Und Unsere Wehrbereitschaft has a colorized version of this artwork.  The original that's been passed down in our family is black-and-white and has 1834 written on the back in what is very distinctly Paulus Roetter's handwriting.