The Forbidden City is definitely a must-see. You should also check out their street markets–they have so much stuff that you can’t possibly see even a half of it in one day. Just beware of spitting people though! The CCTV tower too, perhaps? The Sheraton Great Wall has an amazing interior and excellent service. Definitely check out all of the different structures by Hertzog and de Meuron.
Oddly enough, the place that struck me the most while I was in Beijing was this particular neighborhood that was covered in foliage and extended into the glass walls of a convenience store. I don’t know why but that’s what I would love to see again if I ever go to Beijing again haha. I guess point being, is that sometimes its not in those well-known places that you can find inspiration or something that struck a chord within you. Get lost in the city. My mom and I did (albeit because of our airheadedness), and I must say, it is one of the most memorable days of my life.
Also, you absolutely have to have hainan chicken. It’s usually found in rustic restaurants but may be served in the “finer” restaurants today.