Others exist only as a faint shadow on a photograph taken from the air. At Knockcorragh in County Limerick, a roughly oval earthwork measuring approximately 35 metres by 30 metres has no dramatic monument to mark it, no interpretive panel, no roadside sign. It is the kind of place that archaeology notices before the human eye does, a feature of the landscape that only fully reveals its shape when viewed from above.

The enclosure came to light through aerial survey work, specifically the Bruff Survey, and was recorded in map reference Bruff 272.01 from aerial photograph AP 4/3658. Archaeologist Doody, writing in 2008, described it as a subcircular enclosure and noted that its morphology, meaning its overall shape and form, suggests it may date to the Bronze Age, the broad period running roughly from 2500 to 500 BC in Ireland. Enclosures of this kind are among the more enigmatic features in the Irish archaeological record. They could represent the boundaries of a settlement, an enclosed field, a ceremonial space, or a combination of purposes that changed over centuries. Without excavation, it is difficult to say more with confidence, and the site at Knockcorragh has not, on the available record, been dug. The entry was compiled by Denis Power and uploaded to the record in November 2013.

Because the enclosure was identified from aerial photography rather than from ground survey, a visitor approaching the area around Knockcorragh should not expect to encounter an obvious earthwork. Features of this type are often reduced to low, grass-covered banks or subtle changes in ground level, and in certain seasons, particularly after rain or during a dry summer when crop and grass growth differs over buried features, they become marginally more legible from an elevated vantage point. The relevant maps for the area fall within the Bruff district of south County Limerick. Anyone with a particular interest in the landscape archaeology of the region will find that this site sits within a broader area of known prehistoric activity, where aerial and ground surveys have gradually assembled a picture of a long-settled countryside.