Several small islands break its surface, and Gleneary is among them, listed as an archaeological monument, which means something of human significance once happened here, or was built here, though precisely what remains formally unrecorded in any publicly available source.

Lough Carra sits in a limestone landscape, and islands like Gleneary would have been attractive to early inhabitants for the same reasons that made crannogs, those artificial or semi-artificial island dwellings common across early medieval Ireland, so widespread: relative security, access to fish and wildfowl, and proximity to freshwater. Whether Gleneary carries the traces of a crannog, an early Christian enclosure, or something else entirely is not something the surviving record makes clear. The lake itself is perhaps best known to literary history as the place near which the novelist George Moore grew up at Moore Hall, and where he eventually asked to have his ashes interred on Castle Island. That association at least confirms that Carra's islands have long carried a certain weight of significance for those who knew them.