There is no visible fill between them, just the stones themselves, roughly two to two and a half metres apart, giving the structure the look of a skeletal track rather than a solid road. It runs for at least 240 metres, though overgrowth and spoil heaps obscure where it ultimately leads, and the question of its full extent has not been definitively answered.

The causeway begins at the western end near the pier, just 100 metres east of the Augustinian abbey at Annaghdown, a monastic site with roots going back to the sixth century when St Brendan is said to have founded a settlement here. From the pier, it heads north-east for around 90 metres before bending slightly to run south-east for a further 150 metres. At that point its line becomes harder to follow, but it may have continued southward towards Annaghdown Castle, a medieval structure nearby. The relationship between the causeway and these two monuments, the abbey and the castle, suggests it served as a practical link across ground that would otherwise have been difficult or impassable, particularly in wet seasons when the lakeshore margins flood and the grassland turns to bog. Causeways of this kind, built from locally available stone to raise a passage above soft or waterlogged ground, were a common solution in the Irish medieval landscape, and the limestone geology of the Corrib region made large flat-faced boulders relatively easy to source.