Dear Thomas,
Thanks for the questions.
You are correct that there is a scenic area called Longqingxia near Beijing.
Longqingxia is located at Gucheng Village in Yanqing County. It is around 10 km from Yanqing County and 85 km from Beijing. Longqingxia is regarded as "Small Li River" by local people. Actually, it is a reservior, built in 1973. A dam was built between 2 mountains. In 1991, it was developed as a touristy scenic are and open to publics. Longqingxia scenic area combines southern China's beautiful landscape and Northern China's majestic mountains.
In Summer and Autumn, passengers could do boating on the lake to enjoy the splendid views.
In Winter, there is a Ice Lantern Festival held every year since 1987. Therefore, if your traveling time is limited in China, but would like to see Ice Lantern, this is a good choice.
You could viist to Longqingxia on the day to Badaling Great Wall as they are on the same direction. But if you want to visit Mutianyu Great Wall or other sections of Great Wall, it might need to visit separately.
Hope the above is clear and helpful.
Should you have any further questions, please do not hesitate to let us know.
Best regards
Sophie Huang
Top China Travel