Great Wall of China

 Why It’s Amazing: Millions of people over the course of 21 centuries helped construct, rebuild, and maintain the Great Wall of China, which dips, rises, and bends across the country for some 6,000 miles. The theory that it’s visible from space is now debated, but its immense engineering achievement and man-made beauty are unquestionable.

Secret Viewing Spot: You’ll find the otherworldly ruins of unrestored wall segments in Gubeikou, a less-visited part of the Yanshan Mountain range in the northeast of Miyun County.

When to Go: October’s brisk temperatures and lighter foot traffic make for ideal wall hiking.