Lava Point Campground in Zion National Park!
We loved camping here! The campground is around 7000' so it stays fairly cool even in the blistering heat of the summer. and even if the summer temps are too hot there are plenty of canyons to explore nearby as well as Kolob Reservoir. The most famous canyon nearby is the famous Subway route through the Left Fork of North Creek aka "The Great West Canyon" Due to recent increased popularity the park only allows 80 people through a day combined from both the top down routes and the single approach from Left Fork TH. In order to go through it from top or bottom you'll have to apply for a permit at the NP website and then pick it up at a Ranger's Station before heading in.
The campground itself is pretty small but each has it's own picnic table, fire ring, and mini dumpster. There are 6 campgrounds and they fill up fast, real fast! We got there at noon and by 2 there were no campgrounds left on a Monday in September. Some other awesome bonuses about this camp is that its free and offers a great nearby lunch spot at the namesake Lava Point which is a basalt point that overlooks much of the main canyon of Zion National Park and the West Rim Trail!