Cappadocia - Underground City

A long time ago (presumably before grenades) in a land far away (actually right here, Turkey) underground cities like this were dug with a similar goal to castles: being easy to defend and hard to attack. The place can only be navigated single-file and crouched in many sections (1 ft wide by 3-4 ft high in sections).
Underground cities were 4-8 floors below ground, the size of several city blocks, and had all amenities including baths, kitchens, churches, etc etc.