If you are in Cappadocia with a huge group or during a crowded season, you have to visit the underground cities with many other people. It could be a dreadful experience to stick in the tunnels with the queue in front and back of you. It is because the tunnels are only for one person to walk, and the halls are not enough big for tourist crowd. If you tend to be claustrophobic, I assure you’ll be one, here, in this kind of situation.
We hadn’t experienced this because it wasn’t an over touristy season, but I heard it from many people. If this happens, try to stay calm and breathe regularly. Panic does not solve anything. Or, if you know that you are claustrophobic, do not enter any underground city.
Wherever there is a tourist site, there is a Turkish military for the safety of travelers and tourists and for the security of the national location.