Native American art and ruins, swimming at the falls, and you can even catch fish in the stream.
I've never done the hike to the upper falls, but I've heard good things about that hike also, although it's a lot more exposed.
Highway 12 is one of the best drives in America. We have a Highway 12 camping trip booked in three weeks, but we're not planning to do Calf Creek this time. Hopefully it's not too hot. It's been 15 years since I've last been.