When I can, I let some horses of my equestrian center in the inside arena. They love that! They can unwind and I play with them. We run together, I try to teach them some tricks (count, smile, grab that, follow, backwards) :)
Once a week I try to let him in the inside arena. Most of the time I stay with him as I know he gets bored if I let him alone. We play a little bit, we cuddle, he goes a little bit crazy, it is really funny to see!