Great Wall · Mutianyu

Mutianyu is the green, restored stretch 70km from the city, with 22 watchtowers and far fewer crowds than Badaling. Take the cable car up to Tower 14, hike east toward Towers 19–20 for the steep, dramatic ridge, then ride the 1,580m stainless-steel toboggan back down from near Tower 6. It's hands-down the better day trip — fully walled battlements, forested hills, and that absurd, joyful slide.