The city of Philadelphia is hereby required to maintain and keep open the said Fairmount park for the free use and enjoyment of all the citizens of this state, subject to the rules adopted for the good order and government of the same; and in consideration of the compliance of the said city with the requirements of this act, the state of Pennsylvania hereby declares and agrees, that no railroad shall ever hereafter be constructed within the limits of the said Fairmount park: Provided, That nothing in this act shall be construed to interfere with the rights already acquired by any railroad company whose tracks are now laid within the limits of said Fairmount park.
53 P.S. § 16519