San Francisco City Hall. July 5, 2011

I took this picture of San Francisco’s City Hall on July 5, 2011 – an unusually warm summer day in the city. Nope, City Hall is not a heat exchanger, but it could be a useful “manipulative” (word borrowed from my new-age 4th grade math class) to explain how one works. Just imagine a field of mirrors covering the entire parking lot. 8)