Google's Indoor Maps feature, which launched in November, has been steadily growing with the addition of walking directions and its recent launch in the UK. Today, Google announced the addition of floor plans for 22 US museums and the National Zoological Park, further expanding the Indoor Maps feature. Simply zoom into the museum on Google Maps to see the floor plan, and with "My location" enabled you can get walking directions as well. Some of the museums added include the de Young Museum in San Francisco, the Philadelphia Museum of Art, and the American Museum of Natural History, as well as 17 different Smithsonian Museums (most of which are in Washington, D.C.). Google says that it is currently working with other museums to add maps of their buildings using its Floor Plans tool.