Lough Derg

Lough Derg is about forty kilometres long and up to twelve wide, the third largest lake in Ireland and the biggest on the Shannon, with counties Clare, Tipperary and Galway meeting on its shores. It is not a wilderness lake: it is the centrepiece of the Shannon navigation, and cruisers move up and down it all summer between harbours at Killaloe, Dromineer, Terryglass, Garrykennedy, Mountshannon and Portumna. Holy Island, Inis Cealtra, off Mountshannon holds a seventh-century monastic site with a round tower and several churches, reached by local boat. The eastern shore rises into the Arra Mountains and the Slieve Bernagh hills are on the Clare side, both with walking routes and viewpoints over the water. The lake is large enough to raise a serious sea in wind, and small-boat users get caught out on it every season.

What you actually see

• The navigation - cruisers and harbours the length of the lake.
• Holy Island - a seventh-century monastic site with a round tower.
• The harbour villages - Killaloe, Terryglass, Garrykennedy and others.
• The hills - the Arra Mountains and Slieve Bernagh on either shore.

When to go

May to September for boating and the villages at their liveliest. Out of season much of the hire and hospitality closes. Wind builds quickly on open water.

Honest expectations

A large working navigation, not a quiet lake - it is busy with boats in summer. Wind raises dangerous conditions for small craft. Shore access is patchy; much of the bank is private or reed-choked.

Nearby

Killaloe and Ballina straddle the outflow; Portumna is at the northern end.