It looks, to the uninitiated eye, like the remains of something ancient, perhaps a collapsed enclosure or a long-submerged field boundary. It is neither. It is a deliberately constructed artwork, sitting permanently below the high water mark, where the sea covers and uncovers it according to its own schedule.

The structure was designed by Martin Byrne and Padraig Conway as part of the Solas Atlantis Galway 1993 project, and it is one of three such intertidal installations placed along this stretch of shoreline in the early 1990s. In plan it is roughly subcircular, defined by an outer ring of boulders spanning about 24 metres north to south and a central core of similar construction measuring around 12.5 metres across the same axis. The boulders sit low, only 10 to 20 centimetres above the seabed, and are heavily obscured by seaweed, which gives the whole arrangement a quality closer to geology than to art when seen from the shore. The ring is most legible from the east around to the north-northwest; the remaining arc tends to disappear into the surrounding intertidal texture.

The installation is easiest to read from above. Aerial photographs show the full subcircular geometry clearly, the outer ring and central mass resolving into something that, from altitude, has the composure of a prehistoric monument. At ground level, or rather at water level, it resists that clarity entirely, which may well be part of the point.