永定河
Zhuolu County () is a county in the northwest of Hebei province, bordering Beijing's Mentougou District to the east. It is under the administration of the Zhangjiakou city. It has eight towns, nine townships, and 373 village-level units (). It is located near the confluence of the Sanggan He (桑干河) and Yang He () tributaries to the Yongding River, on the banks of Sanggan He. Zhuolu has 2802 square kilometers (approximately 1082 square miles), with a population of 330,000 inhabitants. Its postal code number is 075600, and its telephone area code is 0313.