The entire site of monuments and churches stretching across roughly 3 kilometers (1.8 miles), was founded by St. Kevin,.
Some structures started from the 6th century. The cathedral (St. Peter and St. Paul) was built in the 10th century with expansion in the 13th century.
The cathedral was not destroyed by Oliver Cromwell's English Parliamentary forces, like most of the castles. It had already been a roofless ruin long before the English Civil War.
In 1214, when the historic diocese of Glendalough was forcibly united with the diocese of Dublin, the complex lost its cultural power, wealth, and upkeep.
The definitive destruction of Glendalough occurred in 1398, when English forces from nearby Dublin attacked and burned the monastic settlement.
The site was further damaged in 1539 during the Dissolution of the Monasteries under Henry VIII.
After the 16th century, all of the churches on the grounds were already completely roofless and ruined.