This stone circle, known as the Lios, is a superb 4000-year-old circular enclosure made up of 113 embanked upright stones. It's the largest prehistoric circle of its kind in Ireland. There's roadside parking and access to the site is free (there's a donation box). From Limerick, take the N24 road south towards Waterford and follow the signs onto the R512 for 16km to the stone circle.
Around 1km further south along the R512, at Holycross garage and post office, a left turn takes you towards Lough Gur, past a ruined 15th-century church, and a wedge tomb on the other side of the road.
