We visited the Elena Gallegos Park on the day of a full moon by accident, and it was absolutely stunning. We were transfixed, quite literally, as the moon made its daily ascent, the mountains ahead of us, and the expanse of the city behind us. It was absolutely stunning.
My only warning - the park closes at 9pm, and they CHAIN the GATES, so makes sure you leave before then. We made the mistake of staying too long (we were hypnotized by the moon), and were LOCKED INTO THE PARK! We ended up having to call 911 to get us out. So beware :o)