What remains is modest to the eye: a weathered rampart rising no more than 1.5 metres, the outlines of a fosse, two roughshod bastions, and a narrow causeway crossing a deep gully to a promontory barely 26 by 16 metres across. Inside the enclosure, the shallow impressions of huts are still traceable. Yet the site was the scene, in November 1580, of a massacre in which some 600 people surrendered and were killed within a single day.

The episode began on 28 August 1580, when a fleet of six ships carrying between 700 and 800 Spaniards, Italians, and Irish, under the command of Sebastiano di San Giuseppe, set sail from Santander. The force was bound for the Dingle Peninsula in support of the Desmond Rebellion, a series of uprisings by the Munster Geraldines against English rule. Dropping anchor in Smerwick Harbour in September, they occupied a promontory where a local man, Piers Rice, had already built what was described as a 'petty castel', and began reinforcing it as a garrison fort with ramparts, bastions, a drawbridge over the causeway, and four gun emplacements. Contemporary plans of the fort, which correspond closely with the earthworks visible today, also show buildings and tents within the walls. The fortifications were not finished before the English response arrived. Lord Grey led the main government force by land, the Earl of Ormond joined him, and Admiral Winter's fleet sealed off the harbour. The siege lasted just three days. Despite having provisions for six months and munitions reportedly sufficient for 4,000 men, the garrison of roughly 600 surrendered on 10 November. All but around twenty, women among them, were killed the same day. Finds recovered from the site include cannon balls, fragments of a cast bronze gun, a lead ingot, and a buckle from a sixteenth-century military uniform.

Local place-names preserve a darker layer of the event's aftermath. A nearby field is known as Gort na Gearradh, the field of the cutting, where tradition holds the victims were decapitated. Their corpses, according to the same accounts, were thrown into the sea, while their heads were buried in fields called Gort na gCeann, the field of the heads, about 500 metres to the south. Bodies that later washed ashore are said to have been buried at Teampall Bán in the neighbouring townland of Caherquin.