How about CYTS Beijing Personal Travel Center? I took a fancy to a two-day tour of the Great Wall and the Forbidden City. 240 yuan per person?

I don't know where you saw it. As far as I know, several well-known travel agencies (including China Youth Travel Service) announced their withdrawal from the one-day tour market in Beijing last month because the black travel agencies in Beijing were so rampant. To be on the safe side, you can sign up at Qianmen and Houhai Beijing Tourism Distribution Center (run by beijing tourism administration), and Badaling can take one day. You can buy a ticket to the Forbidden City and go to Beihai and Jingshan by yourself after visiting the Forbidden City. A two-day tour at 240 is a bit too cheap.