In The Beijinger magazine's Expat Recommended article about Beijing's Best Tour Companies, we're Best for Hiking the Great Wall.

They say:

Skip the touristy sections of the Great Wall such as Badaling and Mutianyu and adventure out to wilder, unrestored sections with Beijing Hikers. Beijing Hikers has been leading hikes to the Great Wall since 2001 and it shows in their well-organised tours. Sections of the Great Wall they visit include Gubeikou, Jinshanling, and Huanghuacheng. Each hike is clearly marked with a difficulty level depending on the length and amount of climbing involved, and you will be accompanied throughout by an experienced guide.

Thanks, The Beijinger!

Read the full list on their website at www.thebeijinger.com/blog/2017/04/17/beijings-best-tour-companies

Other sections in the article include Best for Seeing the Sights, Best for Budding Historians, Best for Art and Design Enthusiasts, Best for Gourmet Travelers, and Best for Something Different.