Wetland platforms of this kind are structures, usually made of timber and brushwood, laid across boggy or waterlogged ground to create a stable working or crossing surface. What makes this cluster of sites quietly remarkable is both its scale and the span of time it represents: the bog has yielded evidence of human activity stretching from the Late Bronze Age well into the Iron Age, a period covering roughly six centuries.

A field survey of Derryville Bog, carried out by Gowen in 1999, recorded the nineteen structures in some detail. Most were built from a combination of brushwood and roundwood, the latter referring to timber used without splitting or squaring, essentially branches and small trunks in their natural round form. In at least three cases, small anchoring pegs were driven in to hold the structure in place, and two platforms were notable for their woven brushwood, a more deliberate form of construction that suggests a degree of craft and planning. Radiocarbon dating was obtained from four of the platforms, placing one in the Late Bronze Age between 792 and 526 BC and another in the Iron Age between 351 and 120 BC. At nine of the sites, the wood species could be identified; alder, ash, birch, hazel and willow were all present, exactly the kinds of trees that would have grown around the margins of a wet, boggy environment and been readily available to those building and maintaining the platforms over generations.