On the eastern shore of what was once Lough Agar, now a dried-up depression in the Galway grassland, a well-preserved ringfort sits on a slight rise and still bears the local name 'Lake Fort', a name that preserves the memory of water long since gone.

A rath is a type of enclosed farmstead, typically of early medieval date, formed by one or more earthen banks surrounding a circular or subcircular interior. This one is more substantial than most. It measures roughly 40 metres east to west and 38.5 metres north to south, and is defined not by a single bank but by two, each revetted with stone to hold the earthwork firm, with a fosse, or ditch, running between them. A well-defined entrance opens at the south-south-east. More intriguing still is a souterrain in the interior. Souterrains are underground stone-lined passages associated with early medieval settlements across Ireland; their precise function is debated, but they are thought to have served for storage, refuge, or both. The local name 'Lake Fort' appears in a 1914 reference by Neary, suggesting the fort was already a recognised feature of the landscape by that point, even as the lake it once overlooked had faded from living memory into place-name alone.