A Celtic cross and a partial round tower. I'm pretty sure this is from Monasterboice, Co. Louth. This was the first place we went in Ireland after getting off the plane in Dublin. It was a beautiful day, although breezy and cool. Monasterboice is the ruins of a monastery and cemetary; you can see the graves in the background. There are three High Crosses here, all dating from the 10th century, but I think this is just a standard Celtic cross grave marker (it doesn't match photos I just found of the 3 High Crosses). There were quite a few in the cemetary. The three High Crosses here are Muiredach's Cross, the West Cross, and the North Cross.
Anyway, there were only two other cars at the site when we were there, so there's a benefit to off-season traveling. Also, free admission. :) However, the public facilities had no toilet paper - the drawback of the off season. You can't go in the tower - it's gated off - but you can walk up the steps to the doorway. This one isn't fully intact; the complete ones have a little cone-shaped roof at the top. The round towers were built as refuges for when the Vikings came raiding. The doorway is on the second level, so the monks could haul everything into the tower and pull up the ladder. Of course, a long seige wouldn't be fun for the monks inside.