I just took my children to Tsinghua/Peking University. There is no limit. You can enter all the doors. Just simply register with your ID card, just like a free park. If I drive by myself, I can't get into the campus. It's inconvenient to park there. I just walked around Peking University and found a parking space at the south gate of Peking University. It's a long way to the classic place of Peking University/Tsinghua. It is recommended to take the subway and get off at the East Gate Station of Peking University, just west of the station.
Beijing
University, straight ahead is Peking University Library/Boya Tower/Weiming Lake/Shifang/Cai Yuanpei Statue/Classic Peking University West Gate. The road east of the station is a classic archway in Tsinghua University. Tsinghua is relatively big, and it is tiring to walk. Pay attention to combining work and rest, hehe.