Longhorn Cavern State Park is in Burnet County. When we visited we didn't have time to tour another cave but we did want to check out some of the impressive work done by the CCC:
This handy historical marker reads:
"Longhorn Cavern opened as a state park in 1932. From 1934 to 1942, Company 854 of the Civilian Conservation Corps (CCC) worked here to explore and develop the cavern. Using hand labor and native materials, the CCC workers built this structure in a style now known as National Park Service (NPS) Rustic. Completed by 1936, the one-story stone pavilion served as administrative offices for the park until 1967. An outside stairway leads to an observation terrace."
And from the observation tower you can get a glimpse of Falkenstein Castle. Yes, there is, in fact, a HUGE castle in the middle of the Texas Hill Country: