The general assembly may authorize the acquiring or taking in fee by the state, or by any cities or towns, of more land and property than is needed for actual construction in the establishing, laying out, widening, extending or relocating of public highways, streets, places, parks or parkways; provided, however, that the additional land and property so authorized to be acquired or taken shall be no more in extent than would be sufficient to form suitable building sites abutting on such public highway, street, place, park or parkway. After so much of the land and property has been appropriated for such public highway, street, place, park or parkway as is needed therefor, the remainder may be held and improved for any public purpose or purposes, or may be sold or leased for value with or without suitable restrictions, and in case of any such sale or lease, the person or persons from whom such remain- der was taken shall have the first right to purchase or lease the same upon such terms as the state or city or town is willing to sell or lease the same.