Yup, interesting, its a very old bridge. This particlar one is actually on the Welsh marches, a place called Clun. on the same river as the famous Iron Bridge. There are still a few of these around in various places in UK, and I felt it could translate to Ireland very easily. Apparently the buttresses are actually places for pedestrians to get out of the way of horses, as its a packhorse bridge, so they have to be hollow as they join the bridge itself. I guessed you would recognise the Jaunting cart.

The greatest part of wisdom is learning to develop  the ineffable genius of extracting the "neither here nor there" out of any situation...."