Moylagh Castle is a small, rough-edged medieval ruin rather than a polished visitor sight. The remains are fragmentary, with a ruined tower and traces of a nearby church, but they give the Oldcastle countryside another layer beyond the Neolithic cairns.
Do not make a special journey for this alone. It is worth a short stop if you are already exploring the lanes around Loughcrew and want one more quiet piece of local history.