Mine is attached to my barn. 16’ deep by 36’ wide, opens to the south and has a 10’ gate separating it from the barn aisle. When the weather is nice, I can open the big barn door and let a breeze go all the way through it, and when it’s cold, closing the big barn door keeps the wind out of the whole place.
Water hydrant is inside the barn, next to the doorway, and my big water trough is inside the run in.
It’s very convenient, as I don’t have to go outside (once I’m in the barn) to manage the run-in.
It’s also pretty close to my house (about 100’, I think), and the outside tackroom door faces the house, which is helpful on bad weather days - no walking all the way around the barn to get in.
My property isn’t set up to allow me to see inside the run-in (house is at the north end of the lot), which I would have liked to do, but it hasn’t been that much of a hardship.
Storage (of some sort or another) is really helpful - an old BO had a big run in that had two bays - one side was for the horses, and the other (accessed by a big sliding door) was for “stuff” - I think the tractor got parked in there sometimes. In any case, when the storage area was wide open, the horses were blocked out of the run-in, but that wasn’t very often, and you could manage that without much trouble - who wants to move stuff around in a rainstorm, anyhow?
As far as site, you have to decide whether you want a run in to be free standing or on a fence line, too. I like the convenience factor (for me) of having my run-in (and barn) on the fence line (I have a walk through gate next to the structure), but I did sacrifice a potential shady spot for the horse(s) by doing it that way. Everything is a bit of a trade off, you just have to decide what you’re willing to give up.
