arrivng at PEK at 12:45am. Have 12 hour layover

US passport coming from Bangkok, arriving in Beijing at 12:45am and departing PEK at 12:45pm onto Dulles.12 hours seems like enough time to leave the airport and do the Great Wall or Forbidden City and I'm interested in doing something like that, but I'm concerned that my arrival time will be prohibitive. #1, can I leave the airport doing TWOV? #2 Is there anything I can reasonably expect to accomplish during my layover given my arrival time? Forbidden City seems unlikely as it doesn't open until 8:30am. I was thinking maybe sunrise at the Great Wall. Do you think that's possible? If so, Mutianyu or Badaling? If not, what can I do at that hour?