It is classified simply as a house of indeterminate date, which is archaeological shorthand for something genuinely puzzling: the site cannot be confidently assigned to any particular period, and nobody has yet been able to say with certainty who built it or when.

What survives is a low earthen bank, no more than 0.6 metres at its highest, tracing a rectangle roughly 12.8 metres east to west and 6.6 metres north to south. At the western end there is a shallow fosse, a defensive or drainage ditch cut into the ground, here only about 0.3 metres deep. Two entrances face each other on the north and south sides, a layout that suggests a degree of deliberate planning rather than casual construction. The position is telling: a broad, level platform overlooking a steep drop to the river below, the kind of spot that offers both prospect and some natural protection. Sullivan, who documented the site in 1994, recorded these dimensions and features, but the question of age and function remains open.

The structure's simplicity is part of what makes it interesting. Earthen-banked buildings of this kind could belong to almost any phase of Irish rural life, from the early medieval period through to post-medieval times, and without excavation the evidence on the surface alone is not enough to pin it down. The Liffey here is far from the wide tidal river familiar from Dublin; at Ballysmuttan it is a narrow upland watercourse running through the foothills of the Wicklow Mountains, and the landscape around this site retains a remoteness that probably looked not entirely different to whoever once came and went through those opposing doorways.