I don't and its very frusterating. I have a flat field thats about the size of an arena (a bit bigger) and is mostly closed off by woods on three sides and our tennis court fence on the other side. But there are two openings so if i fell and my horse decided to run off it could. And also, if it rains I cant ride because i'm afraid my horses will slide in the mud. I jump so its not really safe to jump in a bunch of mud. I would much rather a sand arena. It would be lots easier. Just wondering how many serious riders out there don't have an arena..