The complex includes a large square enclosure of roughly 116 by 138 metres, a prominent D-shaped rise defined by a broad ditch, and a deep oval hollow that opens onto a channel connecting towards the river. That hollow, measuring approximately 25 by 7 metres, is the detail that has drawn particular attention: researchers have proposed it may be a naust, a boat shelter of the kind used by Viking seafarers, its dimensions closely matching Scandinavian examples and the proportions of the Viking longship Skuldelev 2. The site was not identified through fieldwork but through careful examination of Google Earth imagery, and much of what is known about it comes from analysis of a 1932 Air Corps aerial photograph.

The earthworks lie in the townland of Maynetown, known in Irish as An Mhaighean or Moyne, just north of where the Mayne River meets a stream flowing down from the former Baldoyle Racecourse through Seagrange Park. A longphort was a Viking encampment or fortified harbour, typically positioned on a river or estuary to allow the beaching of ships and the raiding or trading of a surrounding territory. The Fragmentary Annals of Ireland record a place called Port Manann under the year 866, and researcher C. Downham has argued that this entry may correspond to a site in this area. The surrounding placenames carry strong Scandinavian associations, and the local topography suggests a former pool immediately south of the earthworks, which would have provided the sheltered water a longphort required. The mid-17th century Down Survey shows a building at roughly this location, and John Rocque's mid-18th century map depicts a D-shaped embankment that is still legible in the landscape today. Later ridge-and-furrow lazybed cultivation, probably 19th century in date, cuts across the earlier features, which helped obscure their significance. Flooding, gravel quarrying throughout the 20th century, and landscaping associated with Baldoyle Racecourse further complicated interpretation.

The site lies in ordinary farmland beside the Moyne Road and is not formally signposted or publicly interpreted. Because it sits on a floodplain, ground conditions can be poor, particularly in winter and early spring. The earthworks are most legible from aerial imagery rather than at ground level, where the subtle rises and ditches blend into the grass. Those visiting the area on foot may notice the slight topographic variation north of the river, but the significance of the complex is not immediately apparent without some familiarity with the aerial photographs. An excavation was carried out in 2022 under licence number 22E050, so further published results may clarify what the ground actually holds.