Hello, I would like to visit the great wall in a 15 hours of connection flight.

You can go to Badaling Geat wall. Take shuttle bus Changping Line to Shuiguan Village station, then transfer to bus Chang 68 to Dengzhuang station, next take bus 879 to Badaling station. It takes around 2.5 hours with CNY38.

Remember to go back to the airport at least 2 hours in advance before the departure.