To give you an idea of what these caverns are like - here's a tractor-trailer driver making a delivery into one in Missouri. There are speed limit signs, stop

To give you an idea of what these caverns are like - here's a tractor-trailer driver making a delivery into one in Missouri. There are speed limit signs, stop signs, directional signs, etc. because otherwise you'll get lost. https://www.youtube.com/watch?v=KDDdgVdczUE https://www.youtube.com/watch?v=KDDdgVdczUE