You can't get rid of real estate you own unless someone else agrees to acquire or take it from you (which, of course, is purely voluntary). You will need to find someone to buy it from you or who will accept it as a gift or donation. Try adjacent or adjoining property owners, who may want more land; developers or builders or contractors, who may be interested in being given or acquring for a low price land to build on; charities, including green space, organizations. But if no one will take it, you will be stuck with it.