Canyons, arches, and waterfalls at Petit Jean State Park
Petit Jean State Park is one of the best state parks in Arkansas simply because it has such a variety of landscapes and things to do. The park is based around Petit Jean Mountain and the rugged bluffs that tower over the Arkansas River and Cedar Creek. Towards the top of the park, there' an artificial lake where you can go fishing or try your hand at kayaking or paddle-boating.
The reason I like Petit Jean State Park so much are the rock formations you can explore. The most famous rock formation in the park is Bear Cave (don't worry, there are no actual bears in sight!). After hiking about 30 or 45 minutes, you arrive at a system of passageways and grottoes that you can explore. Or, try the Seven Hollows trail which take you under one of the coolest natural rock arches I've ever seen.