The Forbidden City in Beijing was the Chinese Imperial Palace for 500 years. Even if you didn't know that, it is very likely you've seen the southern gate of Tiananmen many times, with the portrait of Chairman Mao hanging over it. Today, that's how most tourists will enter the complex (though you don't have to, and I don't recommend it, from the waiting times at security, which don't exist on the east entrance).
Even on a busy day it is possible to see the Forbidden City with very few people in it, as all the organised tours take a route straight down the middle of the complex, from south to north and rapidly exit at the northern gate. So, zig zag from side to side across the complex and you'll find some places seeming almost deserted.
Each section you come to seems bigger and grander than the last - I imagine it was designed that way, to inspire ever-increasing awe at the Imperial home.
Allegedly, there are some days in Beijing with blue skies. I wasn't there to see any such days, but the muted grey pallete of the smog gave a slightly specular feel to the place, with the colours of the giant courtyards reflected in the sky above.
If you want to see the story of the last emperor of China, which includes lots of scenes shots in the Forbidden City, do check out The Last Emperor.