Measuring 8km by 5km, Clare Island manages to cram in two hills, Knockmore (462m) and its little brother Knocknaveen (223m) to the east, behind which the mighty sea cliffs along the northwest shore are home to important breeding colonies of seabirds, notably fulmars. Other rare birds found on the island include peregrines, choughs and barnacle geese, while notable plants include petalwort, a species of liverwort. A leaflet available on the boats details five walks on the island, including a complete circuit which takes about six hours.
The harbour, which shelters a Blue Flag beach with fine views of the mainland mountains, is guarded by a well-preserved, sixteenth-century tower house, which was the main stronghold of Grace O’Malley. In the middle of the island’s south shore near the post office and shop, she – or more likely a relative of hers – is buried in an ornate Gothic tomb in the mid-thirteenth-century Cistercian abbey. More notable from an artistic point of view are the frescoes in the chancel, among the finest extant medieval paintings in Ireland, which depict cattle raids, people hunting and fishing, musicians, dragons and griffins.