The ground is level, the grass unbroken, and there is no mound, ditch, or bank to catch the eye. Yet somewhere beneath the surface lies what was once a ringfort, a circular earthwork enclosure of the kind that early medieval Irish farming families built as a defended homestead, typically surrounding a house and outbuildings with an earthen bank and ditch. This one has been levelled so completely that it leaves no trace at ground level whatsoever.

The enclosure was still legible in 1837, when surveyors working on the Ordnance Survey six-inch map recorded it as a circular shaped feature sitting roughly 45 metres south of the townland boundary with Ballinphort. At that point it was evidently intact enough to be mapped. Sometime between then and now the earthworks were removed, almost certainly through agricultural improvement. What redeemed the site from total obscurity was an aerial photograph taken in November 2011 using Digital Globe imagery, which captured a clear cropmark at the location. Cropmarks appear when buried features, such as the filled-in ditches of a demolished earthwork, affect the moisture and nutrients available to crops or grass above them, causing the vegetation to grow at a slightly different rate or colour, visible only from the air and usually only in dry conditions. The Ballinriddera ringfort is not isolated in its landscape: a second ringfort survives 110 metres to the north, and a third lies 75 metres to the south-east, suggesting this was once a reasonably well-settled patch of Westmeath countryside in the early medieval period.

There is nothing for a visitor to see on the ground, and that is rather the point of the place. Its existence is known only because cartographers recorded it nearly two centuries ago and because a satellite happened to photograph the field under the right conditions in autumn 2011. The monument itself is gone; what remains is the faint biological memory of a ditch that was dug, used, and filled in perhaps a thousand years ago.