The underground cities are literally all over Cappadocia. I have visited the following:
Gaziemir – I visited it by accident, actually. It was not in the tour guide or on hotel recommended maps but the rod signs informed about the “biggest” underground city… Visit the place for 5TL but don’t expect the biggest underground city in Cappadocia It was virtually empty, with no ticket office, only an eldery man hanging around selling the tickets. This city differs from others that it is not that deep but vast and its passageways are big enough for a horse go through. The historians believe this place may have been used as a public house when an invasion ceased to be a threat.
Derinkuyu – is the biggest underground city and most impressive, especially the number of stairs you have to climb down and then up, as there is only one way in both directions. The tour guides speak excellent English and make sure the traffic in the underground corridors is safe. The city apparently goes as deep as 60 m, and was large enough to house ca. 20,000 people with their livestock and food stores.
this city could accommodate around 5000 people. It had a very well built ventilation system, the winery, water cistern and wells, kitchen and storage areas. Storage areas were also built to accommodate livestock, wine and dairy products supplies.