A crannog is an artificial or partly artificial island, typically built during the early medieval period as a defended dwelling place, constructed from timber, brush, and stone in the shallows of a lake. At Lavareen, the feature in question was recorded as a small island of only about five metres in diameter, and even that much is visible only on the 1909 edition of the Ordnance Survey six-inch map. Later inspection found no visible trace of it in the lake.

What lends the site a degree of credibility, despite the absence of any visible remains, is the existence of quernstones recovered from the Lavareen townland. Quernstones are paired circular grinding stones used to mill grain by hand, and they are commonly associated with early settlement sites, including crannogs. A collection of them, attributed to this feature, was acquired by the National Museum of Ireland and referenced by A. T. Lucas in a 1957 publication. The connection is cautious rather than certain, described as probable rather than definitive, but the stones do suggest that something worth recording once occupied this corner of the lough, even if the water or the centuries have since swallowed it entirely.