After surviving devastating attacks by Viking raiders, the monastic university finally succumbed to the assaults of Raymond le Gros in 1173. The castle was presented to Sir Walter Raleigh, who sold it to Richard Boyle, Earl of Cork, in 1602. His son, Robert, the noted chemist and author of Boyle's Law, was born here. Since 1753 it has been the Irish seat of the Dukes of Devonshire, and the gardens are open to the public. The medieval Protestant cathedral dates from 1633, although it was largely rebuilt around 1680.It has soaring Gothic vaulting and still retains in its west wall 9th and 11th century grave slabs from an earlier church.
Catholic cathedral is Romanesque in style.
Lady Louise's Walk along the river and the interesting Town Walk are well signposted. At the eastern end of the bridge in Lismore take the R668 which follows the Blackwater River, then climbs to the pass in the Knockmealdown Mountans known as The Vee and descends to Clogheen, then on to Cahir. Cahir Cahir castle, with its massive great hall, grim dungeon and thick protective enclosing walls, is a superb restoration of the 1142 castle set on a rocky islet in the River Suir. It is also one of Ireland's best preserved castles. Furnishings in the residential apartments are authentic reproductions of the period.