This is a ring barrow, a type of funerary monument consisting of a central mound enclosed by a surrounding ditch, known as a fosse, and often an outer earthen bank. The design was deliberate and precise: the dead, or perhaps just the memory of them, were placed at the centre of a carefully defined circle, separated from the ordinary ground by earth and by water that would have collected in the ditch.

The Johnstown example is modest in scale but well preserved in its proportions. The central mound measures roughly five by six metres and is notably flat-topped, which is characteristic of the type. Around it runs a broad fosse, four metres wide and about a metre deep, with a slight external bank beyond that, bringing the total diameter of the monument to around seventeen or eighteen metres. It sits on a gentle north-east-facing slope, set back about fifty metres from the crest of a ridge, a position that would have given those who constructed or gathered at it an open prospect across the Kings River valley below.