Every such lease shall be for a term of not more than ninety-nine years, may provide for a right of renewal for a like term, and shall contain provision for the improvement of the real estate by the erection of a suitable building or buildings of dignified and appropriate architecture, absolute ownership of which building or buildings shall revert to the city, free of any claim or charge, at the end of the term of the said lease or any renewal thereof.
53 P.S. § 1402