"The Nushabad Underground City near Kashan, Iran, stands as a 1,500-year-old marvel from the Sassanian era. Carved an impressive 4 to 18 meters deep across three levels, this labyrinth stretches over 4 square kilometers. Its intricate network of tunnels, rooms, and air ducts provided refuge for locals seeking shelter from invaders like the Mongols and Arabs. With hidden entrances tucked beneath homes and forts, plus cunning traps like narrow curving passages, it safely housed thousands for days, complete with wells and storage."