If you don't like the weather in one part of Westcave Preserve, you might like it better in another: Up to a 25° difference in temperature has been recorded between the highest area of this beautiful natural habitat, an arid Hill Country scrub, and the lowest, a lush woodland spread across a canyon floor. Because the ecosystem here is so delicate, the 30 acres on the Pedernales River may be entered only by guided tour. Reservations are taken for weekday visits, while on weekends, the first 30 people to show up at the allotted times are allowed in.