Old Tunnel State Park, a 16.1-acre site on Old San Antonio Road between Fredericksburg and Comfort, is the smallest state park in Texas. Opened to the public in 2012 and managed by the Texas Parks and Wildlife Department, it preserves a 920-foot railroad tunnel built for the Fredericksburg and Northern Railway, much of it dug by hand through limestone. Trains used the tunnel until the line was dismantled in the early 1940s and its rails removed for the World War II effort. The abandoned tunnel later became home to a major bat colony, and from May through October its evening bat emergence draws visitors for organized viewing programs.