Visited 13/5/19. Was only there a couple of minutes when the farmer +1 pulled up in his little buggy pick up type thing and told me in no uncertain terms "get out of our fucking field".
I gave him a thumbs up and quickly jumped on the very timely approaching bus.
Nice!
It's tall, has buckets of lovely lichen and moss, and despite the sheep protector fence (I assume it's there to prevent sheep from rubbing the stone and making it fall on them), it has an air of stateliness. It knows that it gets seen from the road, and is self assured in it's role as the blocking stone of Maeshowe.
Take the time to stop and get out of the car, or nip over if you're at the stones of Stenness, it's not far, though the main Kirkwall-Stromness road is busy at times. It can be easily reached through the gate, though as Kammer suggests there is no path. I tried to check for permission with the house directly across the road, but no-one was in (or not answering).
Probably not good for wheelchair users, or anyone with mobility issues.
Visited August 1997: With all the megalithic action going on in this area, the little old Barnhouse Stone gets a bit neglected, and looks a rather sorry for itself sitting in it's enclosure.
I'm afraid I can't remember much about how we got to the stone, or where we parked. I think the visit involved climbing over a gate and wondering across a field. Having looked at the map I'm guessing that there's no footpath to the stone.