Last week, the friendly folks at The Hutong invited me to return to Gubeikou (古北口, or “Ancient North Pass”), a section of the Great Wall of China about two hours northwest of Beijing. Jeremiah and Simon, the trip's leaders, brought a wealth of knowledge of this region's history and natural setting. They did a great job of explaining the circumstances that led to the wall's construction in the 16th century. When I went to Gubeikou without a guide, I simply hiked on the wall. But this time, I could really envision Manchu armies invading from the north, and Chinese troops taking positions to defend their homeland.