To travel to Turkey, you must go to Cappadocia. To Cappadocia, three things must be done: hot air balloons, underground cities and cave hotels. There are many underground cities in Cappa, and the Kaymakler underground city is very well protected and developed. It is said that there are more than 10 floors underground, we just walked to the 8th floor underground, and we dare not go down again. The ventilation system is designed very scientifically and has no underground feeling at all.