Glendalough is known as the valley of the two lakes. This place is renowned for its Early Medieval monastic settlement, which was founded by Saint Kevin in the 6th century. Kevin was a descendent of a ruling family in Leinster. He studied under three holy men named Eoghan, Lochan, and Éanna. It was said in the legends about Kevin that at this time he went to Glendalough and lived in the hollow of a tree. Later in his life he returned to Glendalough with a group of monks to create and found a monastery. He attracted many followers as his fame as a holy men spread. He died in 618, but afterwards the town flourished for 6 centuries with references for the Irish Annals of the deaths of abbots and raids on the settlement.
In the year 1111, at the Synod of Ráth Breasail, Glendalough was made one of the two dioceses of North Leinster. The abbot of Glendalough became Laurence O’Toole who was well known by many for his sanctity and hospitality. Although he was appointed the Archbishop of Dublin in 1162 that did not stop O’Toole from visiting Glendalough occasionally to enjoy the solitude of Saint Kevin’s bed. He died in 1180.
The dioceses of Glendalough and Dublin were joined in 1214. After that the cultural and religious status of Glendalough diminished. There was an attack on the monastery in 1398 by the English forces that left it in ruin. However, it continued as a church and a place of pilgrimage. The references that describe it during the 18th and 19th century portray it, on occasion, as a riotous assembly especially during the feast of Saint Kevin on the third of June.
Today, what remains of Glendalough is only a small part of what would have been there. When the monastery was at its prime there would have been workshops, areas for manuscript writing and copying, guesthouses, an infirmary, farm buildings and homes for both the monks and large populations. The buildings that survive today such as the cathedral, the gateway, and the round tower probably date back to the 10th and 12th century.