In a level pasture near Thomastown in County Kildare, there is nothing to see. That, in a sense, is precisely what makes this site worth knowing about. Two small circular enclosures lie beneath the grass, their existence confirmed not by any upstanding wall or earthwork but by the differential growth of crops above them, patterns legible only from the air and captured in a single aerial photograph.

Cropmarks form when buried features, such as ditches, walls, or pits, affect the moisture and nutrients available to plants growing above them. Soil that once filled an ancient ditch tends to retain more water, producing a lusher, darker strip of growth; buried stonework does the opposite, stressing the plants above it. The result, visible in dry summers when contrast is highest, is a ghostly plan of structures that have otherwise vanished entirely from the surface. At Thomastown, the photograph in question, catalogued as GSI N 375-7, reveals two such circular forms side by side on flat ground. Circular enclosures of this kind are common across Ireland, often associated with early medieval settlement or ritual use, though without excavation the precise date and function of these two examples cannot be established.

There are no surface traces surviving at this location, which means a visit would offer the eye nothing to fix on. The significance of the site is entirely photographic and archival, belonging to that large category of Irish archaeology that is known to exist but invisible to anyone standing in the field above it.