The board of park commissioners of any city of the first class shall have the power to acquire by purchase, gift, condemnation or otherwise such lands as they may deem necessary for public parks outside of the corporate limits of the city and not to exceed one mile therefrom, and to issue and sell, subject to the limitations of this act, general bonds of the city to pay therefor: Provided, That the board of park commissioners of any city of the first class having a population of more than 80,000, shall have the power to acquire by purchase, gift, condemnation or otherwise such lands as they may deem necessary for public parks outside of the corporate limits of the city and not to exceed five miles therefrom and to issue and sell subject to the limitations of this act general bonds of the city to pay therefor.