《水经注·卷十三》
沧河又往西流经居庸县老城南面，那就是魏时的上谷郡治。
沧河又西径居庸县故城南，魏上谷郡治。
The Cang River flows westwards, past the southern face of the old city of Juyong County. This was the site of the Shanggu County government during the Wei Dynasty.