A seat of high kings
Before Patrick's arrival, Ireland was largely a pagan land. So it's safe to say he had his work cut out for him on his mission! But he was not deterred. During Bealtaine, the pagan feast celebrating the summer solstice, the high king lit a fire at his seat on the Hill of Tara, County Meath. In defiance, and to celebrate Easter, St Patrick lit his own fire nearby on the Hill of Slane. The king's guards were immediately ordered to investigate who had started the blaze. Patrick performed one of his many miracles, and cast an illusion over him and his followers to appear as a herd of deer. Making his way to the king's seat, he made his case to the king. Through his preaching and debating, Patrick converted many of the king's court to Christianity. Not only that, he impressed the king so much that he allowed him to walk free to continue his mission across Ireland.
If you have more time
A short drive away, Brú na Bóinne gives a glimpse in to pre-Christian Ireland, before Patrick's arrival. Huge passage tombs that predate the pyramids, including the world-famous Newgrange, cover the landscape and feature incredible displays of ancient megalithic art, carved in to the rocks themselves.