One of the most incredible things I saw while exploring Beijing was the Underground City, also known as Dixia Cheng. It is a series of tunnels compromising a bomb shelter that was constructed in the 1970s in anticipation of a nuclear war with the Soviet Union. Thank goodness it never needed to be used for that purpose. I spent an afternoon doing some urban spelunking and wandering the tunnels with my Hasselblad. The tunnels were dark and damp and filled with some odd artifacts, like a series of folding chairs with framed portraits of communist leaders, including Joseph Stalin, Mao Zedong, and Chiang Kai-Shek. There is even a portrait of Karl Marx that from a distance looks like Frederick Douglass.