The Glyde rises in the town of Bailieborough in Cavan, the upper reaches are sometimes known as the Lagan River, but after the Killanny River joins, exclusively as the Glyde. Another tributary is the River Dee. The Glyde flows in a south-easterly direction before entering the sea at Annagassan in Louth, site of the recently rediscovered ninth-century Viking longphortLinn Duachaill.[2]