Natural Bridge Caverns is a major limestone cave system about half an hour west of New Braunfels. Guided routes descend through large chambers of stalactites, flowstone, columns, and damp, warm air that feels very different from the dry Hill Country above.
The cave is commercial and family-oriented, with above-ground activities attached, but the underground formations are the point. It works well as a half-day trip from New Braunfels, especially when river crowds or summer heat make staying above ground less appealing.