These maps from Borch are durable, water-repellent and feature a laminated write-on/wipe off surface.  With an enlargement of downtown Beijin, the Forbidden City, the Summer Palace, Badaling, Fragrant Hills Park, and Chengde as well as the public transportation lines this is a great map to add to your packing list.  Measuring approximately 9.5"x4.5" folded up it unfolds into a flat double-sided map measuring 34"x19.25".