Explore eighteenth-century Beijing — the Forbidden City, temples, and hutongs — on 乾隆京城全図 brought to the digital world by Toyo Bunko. Click thumbnails on the overview map to access high-resolution images.
http://dsr.nii.ac.jp/toyobunko/II-11-D-802/V-1/page/0001.html.en
The map can also be viewed on Google Earth
http://dsr.nii.ac.jp/geography/historical-maps/toyobunko/II-11-D-802/1.0/all.kmz