Natural caves (especially limestone) are usually stable as it takes millions of years for them to be carved out by natural underground water. The soft stuff gets removed and the hard stuff remains. If its been that ways for centuries, its not likely to change over short time spans.
Manmade tunnels like for mining, in contrast, are much less stable and prone to cave-in. They don't take into account the natural erosion processes of natural caves, they cut through soft and hard earth, and stress or sudden changes in ground water can cause collapse.
If they try to dig out or widen the tunnels, it could just cause a catastrophic collapse.
Looks like there may be places where air pressure is keeping water levels down.