The ringfort at Reerasta South sits on a gentle rise in County Limerick, a roughly circular enclosure about 53 metres across, its banks worn down in places to little more than a scraped edge. Nothing about its appearance today would suggest it once held what scholars consider the finest piece of eighth-century metalwork to survive from Ireland.

In late September 1868, the son of a widow named Quin was digging potatoes near the south-western side of the fort when his spade struck something hard close to the roots of a thorn bush. He reached in and pulled out the pin of a fibula, a type of early medieval brooch, then dug down to roughly three feet and found a large silver cup laid in the earth, protected on one side by a rough flagstone. Inside it sat a smaller bronze cup and four more brooches. That silver vessel was the Ardagh Chalice, now held in the National Museum of Ireland under accession number 1874:99. The Earl of Dunraven, writing in 1869, recorded the find in detail and also noted a grimmer piece of family history: widow Quin told him that around twenty years earlier, another chalice, described as gold, had been turned up about fifty yards to the west while tilling. Her children, she said, had taken it outside to play with one day, and she never saw it again. Dunraven also noted that the fort had already been partly levelled for tillage by the time he recorded it, and that a large local standing stone, known as Reerasta Cloch, which had been built into the outer face of the bank, had been broken up sometime before his visit.

The site is a national monument and sits immediately south of a public road that marks the townland boundary with Ardagh, with a compound housing two water towers to the north-east. The earthen bank, a fosse (a defensive ditch) running around much of the exterior, and a low curving bank to the west that may represent a second, outer enclosure are all still visible on the ground, though sections of the fosse are heavily overgrown. The interior dips gently towards the centre and carries a shallow depression to the east of centre. The first edition Ordnance Survey map depicted it as a bivallate ringfort, meaning it originally had two concentric enclosing banks, and the surviving townland boundary curving around the south appears to follow the line of that outer ring.