On the edge of the Shannon Estuary, battered by Atlantic winds, stands Carrigaholt Castle – a five-storey tower house that has endured for more than five centuries. Built around 1480, this was no stately home. It was a fortress, pure and simple.

Its design left little room for comfort. Narrow spiral stairs slowed the advance of intruders, sheer walls offered no easy purchase, and a murder hole above the entrance allowed defenders to rain down rocks, boiling water, or worse on unwelcome visitors.

Carrigaholt was the stronghold of the MacMahons, who held it for generations and survived countless attacks. Their most infamous episode came in 1588, when Teige Caech MacMahon is said to have captured shipwrecked sailors from the Spanish Armada. The reprisals that followed drenched the land in blood and added another chapter to the castle’s warlike reputation.

In 1603, the stronghold passed to the O’Briens of Thomond, before Crown grants eventually placed it in the hands of the Burton family in the 18th century. The Burtons lived here into the 19th century, long after its defensive purpose had faded. Today the ruin is maintained by the Office of Public Works – though access inside is strictly forbidden.

For some, this prohibition is nothing more than a safety measure. For others, it is something darker.

Local legend claims that one chamber in the castle holds a presence so malevolent it had to be sealed away. In the 1920s, a man – sometimes described as a priest, sometimes as an exorcist – entered the room determined to banish the evil within. He carried only holy water, a crucifix, and his faith. By morning he was dead. His body was found stiff with terror, his face locked in a scream so dreadful that no one could bear to look upon it. The chamber was bricked up soon after, with warnings that it should never again be opened.

Skeptics insist the castle is simply closed because of its ruinous state. But many locals will tell you otherwise: that something truly diabolical remains sealed inside those walls.

Carrigaholt’s supernatural reputation does not end there. As early as the 1870s, stories were told of phantom soldiers appearing in the fields surrounding the ruin. On winter nights, lines of ghostly troops were said to march in formation before vanishing at dawn into the estuary’s waters. Antiquarian T. J. Westropp recorded these tales in 1875, describing how “the ghost of Lord Clare” was believed to muster his spectral dragoons before the ruined fortress.

Other legends drift in from the sea. In the 1930s, a Limerick sea captain claimed he landed on a nearby island dotted with cottages, where he was welcomed into a home for tea. Yet as he departed, the island he had just visited dissolved before his eyes – vanishing completely.

And off the west Clare coast, there are still whispers of a sunken city called Cill Stuifín, glimpsed only in rare light or at the lowest tides. Some say it is an optical illusion. Others swear it is a drowned settlement, forever hidden beneath the waves.