Tempe Beach Park - such a gem in our landlocked State...
Sure, it's a man-made water source, and yes - it's pretty nasty if you plan on swimming inside Tempe Town Lake, but it's gorgeous during the day and at night too!
I've done a handful of triathlons that started and ended at Tempe Beach Park, and most recently, I did the PetSmart Walk (go team Yelp) that took place at the park as well...
With the proximity of the park to ASU / Mill Ave, it really is a fun place to go hang for an afternoon - no matter what's going on there...
My only words of wisdom - don't swallow the lake water!