Originally Posted by jiejie

That's not entirely true. Mutianyu has plenty of steep sections once you get up there, even on the restored part, and if you walk away from the central tourist part of the wall by the cable car and chair lift, towards Jiankou, you can get to more unrestored parts and also lose most of the other people.

If you get an early start around 07:00 from central Beijing and get to Mutianyu about when it opens, you can have a fairly tourist-free experience for the first hour. Come down around 11:00-11:30 and have driver take you to Summer Palace east gate and drop you off. You won't go through central Beijing to do this. Assuming a quick lunch either at Mutianyu or near the Summer Palace, you should be able to hit the SP between 13:30 and 16:30 then exit the north gate and make your way to the subway to get back to center of town and wherever your hotel is. Or find an empty taxi if you can. Having the driver wait around for you and pick you up at another SP gate is possible but adds to the cost.