To tell the truth, this is a tragedy for you. I am also a junior in Peking University. According to my experience, there is basically nothing interesting, but I will introduce you to Golden Beach (camping, barbecue), Silver Beach, Yeli Island, Mystery Island, Pearl Paradise and Qi 'ao Island (I went there by bike last time). After that, you can go to a buffet, such as Mongolian sheep, haha, almost.

Ps: This is a good time to socialize. If there are many boys in your class, contact the class with many girls to socialize. This is the key. The happiness of your class is in your hands.