Both Peking University and Tsinghua are located in Haidian District, Beijing, and they are not closed.
How many entrances are there in Tsinghua? Wudaokou East Gate near Wudaokou subway station (this gate is called the East Gate, actually facing south), and the West Gate of Yuanmingyuan, where people come and go, is in the north of Zhongguancun.
Peking University and Tsinghua are separated by a smart road, and you can reach Peking University by going south from Tsinghua West Gate.
The postcode of Tsinghua is 100084, not 10008 1.