Russell cave national park
Russell Cave is the 3rd longest mapped cave in Alabama, at 7.2 miles and the surrounding 14,000 acres of land drain into the cave so it floods very fast, and also drains almost as fast. I would not wanna be caught in there during a storm.
Unfortunately this was as far as I could go inside because the NPS was renovating the trail. I definitely plan on going back though.
Natural bridge park
According to the sign at the entrance: "The Natural Bridge is the longest rock arch east of the Rockies. It was formed 200 million years ago when the sea washed the sandstone away, leaving iron ore veins holding the bridge."
This was fun to explore. There was no one there except me and it took about an hour to hike the 1.3 mile trail which included three large natural caves and a mini-waterfall. My only disappointment was that I didn't bring the wide angle lens.