Archaeologists have discovered a Bronze Age pit built from large stone slabs on Sligo’s Coney Island.

Experts believe the box-like structure, measuring about a meter long and 80 cm wide (3' x 2.5'), could have been used for bathing or cooking 4,000 years ago.

It is thought to be part of a fulacht fiadh, a prehistoric trough or pit dug into the ground and filled with water. Heated stones would be added to bring the water to boil.

Eammon Kelly, the director of Irish Antiquities at the National Museum, led the excavation team. The structure was identified as an archaeological site by IT Sligo student Ciaran Davis, who alerted the museum.

“It tells us that people walked the beach here 3,000 or 4,000 years ago, searched for large stone slabs, and carefully built this structure,” said Davis, an archaeology student. “Many other archaeological sites probably await discovery on Coney.”

Dr Marion Dowd, a lecturer at IT Sligo, said that while there are thousands of similar Bronze Age structures throughout Ireland, it is rare to find one on a beach.

“I know of one other example in Cork. It makes us wonder why they would have wanted to heat saltwater.”

Read more: New bog body found by peat worker most likely from Bronze Age

Dr Dowd said locally the structure has been known as the “lovers’ wishing well” and the belief was that anyone who lay inside it would dream of the person they would marry. It was also known as “the sailor’s grave.”

Only one family lives on the island full-time, but there are a number of holiday homes on Coney, which is also popular with day trippers.

As the structure had been known to local people for decades, Eammon Kelly told the Irish Times the it was “quite extraordinary” that is had remained undisturbed for so long.

“It shows the absolute respect the community has for it, perhaps because some thought it was the grave of a sailor,” he said. “But we have seen grave sites elsewhere which were plundered.”

The researchers will use radiocarbon dating to determine the exact age of the structure.