There are things to do on campus, but there could be more. Arcade rats and pool junkies love the Union, which is always crowded with people doing all sorts of things. One part of the Union that's often overlooked is the Music Listening Room, which a lot of students don't use. The rest of the building is almost always packed, mostly with people relaxing or studying. The Union is the focal point of student life, with the Riverfront Center coming in a close second. Riverfront Center is basically all eateries, so it's naturally a hotbed of activity. However, the Union has more than just food, and pretty much all of the recreational options are located there.
Athletic facilities are open to students, but not all day. The weight rooms, swimming pools, gym, and racquetball courts are only open at night, so unless you have some kind of physical education class, you won't have too many options for physical activity during the day on campus.