The new Cahaba River Park off County Road 13 near Helena.
It has two pavilions with rest rooms (running water), canoeing, fishing, kayaking, hiking, mountain biking, swimming. There are 13 miles of sing track and more than 5 miles of double track hiking and biking rails, and now Geocaching.
The difficulty of these caches is raised a bit because cell phone reception is iffy. You may need to go old-time with an antenna or the trusty Magellan or Garmin. With one of these in hand, the caches should be fairly easy to find.
The terrain is higher because you are going to need some tools (readily available) to reach it.