There is very beautiful, old residential area which is well-worth seeing and a very nice, large park in the same area with a big lake. See http://www.riversideca.gov/PARK_REC/facilities.asp

I was at a University of California Riverside event a few years ago and was pleasantly surprised at Riverside. The older parts are lovely remnants of the time when California dreamed big.

The UC campus is also an interesting showcase of modern buildings.