In reply to Erstwhile:
I find Arco campsites too big and the town less interesting in the afternoon heat or evening. But yes, the climbing shops are in Arco, Riva is more about wind surfing and mountain biking, but the distance is very short. The campsite before the swimming pool in Arco is noisy and full of locals staying there for their entire holiday. I guess the campsite behind the swimming pool in Arco is more quiet and spaced out, but worse facilities. You need a car to get to pretty much any crag around Arco, so I tend to stay by the lake. As I said, the campsite next to the beach means you can swim in the afternoon and have dinner in Riva. This campsite is really small so locals do not favor it but there are more wind surfers there than you find in Arco campsites. When you drive 5-10km east from Riva, there is a beautiful campsite on the hill, in an olive grove, it used to be more hippy in attitude than any of the other campsites in the area
But most importantly, call and book beforehand, all these campsites get completely fully booked July-August-September