Great Wall of China
With only a small portion of the wall actually open to the public even this shows what an epic acheivement the wall is.
Getting There
There are several areas that are typically visited by tourists from Beijing. It is recommended that, if time allows, you visit the Mutianyu section of the great wall which is slightly less touristy than the (much closer) Badaling section. Tours regularly operate from Beijing as a taxi visit is not recommended (it is not THAT close!).
The Mutianyu section also has a ski lift that takes you from the car park to the wall which is highly recommended (it is quite a climb otherwise).
Getting to the Wall
Be aware that you WILL be approached to buy any manner of tourist souvenirs on approaching and leaving the wall though on the wall itself you can enjoy a bit of a break from it (well, you will have to deal with all of the people though…).
Do not underestimate the effort involved in climbing around on top of the wall and be sure to wear good footwear.