This uninhabited, windswept and treeless island in the estuary 3km southwest of Kilrush was the site of a Christian settlement founded by St Senan in the 6th century. Its 36m-high round tower, the best preserved in Ireland, has its entrance at ground level instead of the usual position high above the foundation. The evocative ruins of six medieval churches include the 9th-century Cathedral of St Mary (Teampall Naomh Mhuire) – part of St Senan's Monastery.
Also here are a lighthouse and an artillery battery, built during the Napoleonic wars, at the southern end of the island. A free exhibition on the history and wildlife of the Heritage Service–administered island is housed in the Scattery Island Visitor Centre. The centre also provides free 45-minute tours to St Senan's Monastery.
Scattery Island Ferries runs boats from Kilrush to the island; the journey takes 15 to 20 minutes. There's no strict timetable as the trips are subject to tidal and weather conditions; visits usually last about one hour. Buy tickets at the small kiosk at Kilrush Marina and bring a decent pair of walking shoes.