Hill Country, near San Antonio you will find America's largest privately operated caverns, known as the Natural Bridge Caverns.
Natural Bridge Caverns are adjacent to the Natural Bridge Wildlife Ranch, which is a drive-through animal safari park.
Somehow Natural Bridge Caverns was not discovered by Texans until found on March 27, 1960 by four students from San Antonio's St. Mary's University. The caverns were located on land owned by Mrs. Clara Wuest. Negotiations with both the National Park Service and the Texas Park System had both entities agreeing the caverns should be developed as a public attraction, but neither agency had the funds to make it happen.
So, Mrs. Wuest developed Natural Bridge Caverns as a privately funded enterprise, which opened on July 3, 1964.
You can go to the Natural Bridge Caverns website for all the information about various activities in the Natural Bridge Caverns complex, along with pricing.