Beijing's Ancient Observatory is a small but memorable science museum on a surviving section of the old city wall. The observatory was founded in the fifteenth century, and its rooftop platform still holds large bronze astronomical instruments that look part scientific tool, part imperial sculpture.
Inside, exhibits explain Chinese star maps, calendar-making, and the long exchange between Chinese and Jesuit astronomy. It is a good stop if you want a quieter Beijing sight with real historical depth, especially after the larger palace and temple circuits.