The structure is a hut site, the surviving trace of a simple prehistoric or early medieval dwelling, and its diameter measures roughly four metres. That modest circuit of material, worn down to little more than a grassy ripple in the ground, is all that remains of what was once someone's shelter.

Hut sites of this kind, defined by a low earthen or stone bank enclosing a circular floor area, are scattered across the Irish landscape and represent some of the most unassuming yet quietly persistent evidence of early human settlement. The circular form was the standard building approach for much of prehistoric and early medieval Ireland, with walls constructed from whatever combination of stone, turf, and timber the local terrain offered. At Johnstown, the bank of stone and earth suggests a structure that relied on the materials immediately to hand on that Wicklow hillside. The site sits near the southern foot of a ridge, a position that would have offered some shelter from prevailing winds while keeping the ground workable.