What survives is a court cairn, a type of megalithic tomb built by farming communities in Ireland roughly five thousand years ago, characterised by a roofed burial gallery approached through an open, semicircular forecourt where ritual activity is thought to have taken place. At Colladussaun, that forecourt and the cairn that once enclosed the chamber are still present, though both have been pulled into the ordinary geometry of a working agricultural landscape.

The cairn itself measures eighteen metres east to west and eight metres north to south, rising to about one and a half metres, and is now subrectangular in plan. Its northern and eastern edges are defined by straight field fences, and at least one upright stone appears to have been incorporated directly into the boundary wall running east to west along the north side. The court survives at the north-east corner of the cairn, where six contiguous orthostats, the large upright slabs that form the structural skeleton of such monuments, remain standing in a south-facing arc. The largest of these, at the western end, is just over a metre long and eighty centimetres high, with the remaining five stones diminishing in size toward the east. A short distance to the north of this arc, three further orthostats may mark the entrance to the burial chamber, which probably extends north-westward through the body of the cairn. An isolated upright protruding from the cairn about five metres to the west of those possible entrance stones may represent the chamber's back stone. Two large stones lying at a slant within the court area may be displaced capstones, the flat covering slabs that would originally have roofed the gallery.

The site is heavily overgrown, which makes individual stones difficult to read and the overall layout hard to follow on the ground. The field fences that now bisect and border the monument are a reminder of how thoroughly later land division has rearranged the context of prehistoric sites in the west of Ireland, folding them into boundaries and margins without quite erasing them.