An underground city is a network of tunnels that connects various buildings below the street level. These may include office blocks, metro stations, underground shopping malls.
Underground structures or networks are usually found in countries with cold climate. For example, the temperature in Canada in winter is -10 degree Celsius. The climate in Canada does not permit free movement over ground. That is the reason for the development of underground cities. Montreal’s RESO is the world’s largest Underground city in Canada. It is popularly known as “Double Decker City“.
Underground cities usually have entrances through public spaces. The underground structure rises over ground and provides for a proper entrance to the underground structure.