Soon after proclaiming Christianity in Ireland, St. Patrick built a church here on land granted to him by the son of the High King. He built it near an ancient ford that crossed the river just beyond the bridge and it was from this that Trim got its name.
Surrounding the Castle are fascinating ruins which provide evidence of fervent religious activity. Stone relics abound in St. Patricks Cathedral, its church and porch revealing a number of medieval graveslabs. St. Marys Abbey is the remains of an Augustinian monastery founded in the 12th century and later a focal point for pilgrimage.