Glendalough

Glendalough needs 1 day: touring the ruins of the monastic settlement founded in the 6th century by St. Kevin, with its nearly intact round tower, and walking to the upper lake between mountains, in a single day. April-September brings the best weather. It's inexpensive, a common day trip from Dublin, just over an hour away. It was one of the great centers of monastic learning in early medieval Europe, drawing students from across the continent for centuries, and its round tower, over 30 meters tall, built as both refuge and bell tower, is one of the best-preserved examples of this type of early Irish architecture.