Went to the Forbidden City and the Great Wall before the AC meeting today. It was absolutely chucking it down with rain, but both are spectacular. I'll edit and upload the Great Wall photos tomorrow if I have time.
Everything in the FC is arranged in threes, there's 3 levels of terrace inside the compound, 81 nails in every door, 9999 rooms and so on. It's properly large, about 1 sq km and it was packed with Chinese tourists, even in the rain.
Having seen more of it now, I can see that Beijing is seriously big, it's almost eight times bigger than Tokyo, fifteen times bigger than LA, and hundreds of times bigger than London. The tourguide described Beijing as "quite small really" - there are 25 cities in China that are bigger still. The scale of this place is amazing.