65 ILCS 5/11-121-1

Every municipality may construct or enter into contracts for the construction of or to otherwise acquire in, under, upon, across, or along the streets, alleys, and public places of the municipality, and in, under, and upon any other property owned by the municipality or leased to it for the purpose, subways for local transportation and other public utility purposes and for any other municipal purpose. The term "subways" as used in this Division 121, includes all tunnels, entrances, exits, passageways, connections, approaches, inclines, elevators, stations, and other structures, equipment, appliances, or appurtenant property, appropriate to a system of such subways.