65 ILCS 5/11-75-1
Every municipality has the power to lease the space above and around buildings located on land owned or otherwise held by the municipality to any person for any term not exceeding 99 years.
Every municipality has the power to lease, in the same manner and for a similar term, any space over any street, alley, or other public place, in the municipality, more than 12 feet above the level of the street, alley, or other public place, to the person who owns the fee or a leasehold estate, for a term not less than that of the proposed lease, in the property on both sides of the portion of the street, alley, or other public place so to be leased, whenever the corporate authorities of the municipality are of the opinion that that space is not needed for street, alley, or other public purpose, and that the public interest will be subserved by such leasing. The leasing of such a space shall be authorized by ordinance. In this ordinance the lease and its terms shall be set forth with reasonable certainty.
65 ILCS 5/11-75-1