From Simatai Section to Ming Tombs.

To my experience, it is too tight to visit both Simatai and Ming Tombs in a day as the tranportation is not very convenient. From downtown area, you can take bus 980 or 980 Express at Dongzhimen Station and get off at Miyun Bus Station, then transfer to bus Mi 37, Mi 50, or Mi 51 to Simatai. If you want to visit both, I think you would better charter a car instead of taking public transportation.