I'm not sure - it was a few years ago that I visited and back then I wasn't in the habit of taking on-site notes like I do now. Achnabreck is itself close to a hilltop, and its views look out to the north over the remarkable flatlands that are the Kilmartin valley. Perhaps Dunadd or the Barr are the hill you're looking for, though... I bet someone else knows.

You'd love it there, by the way, its a beautiful, peaceful place. It feels entirely removed from day-to-day life, just the sound of the wind in the trees...

(really gotta go now!)