The Caverns of Sonora, a protected show cave about 8 miles west of Sonora in West Texas, is renowned for the extraordinary abundance and purity of its calcite formations, especially helictites, and is recognized as a National Natural Landmark. Formed in Segovia Limestone through acidic groundwater processes millions of years ago, the cave later developed spectacular speleothems, including the once-unique Butterfly formation. Known locally as Mayfield Cave in the early 1900s, it was greatly expanded by cavers in 1955, then protected and developed for guided tours under Jim Papadakis, opening in 1960. Today, developed trails provide controlled access to one of Texas's most celebrated underground landscapes.