Except… they’re not.
Here’s one of many underground cities (in what is now Turkey) built over 2,700 years ago. Check out the maps!
Over 280 feet deep. Sealable stone doors. Irrigation system. Ventilation shafts. Escape routes. Wells. Connections to other underground cities.
Human ingenuity and Iron Age tools built this. Without magic. So the next time some elitist poo-poos your dungeon-crawling adventures as “unrealistic,” tell them to head to Cappadocia, Turkey for a guided tour of an “unrealistic” underground city.