The lake lies at the gates of the city of Varese, between the Morainic hills of the foothills of the Alps in the high Po plain. It was created when a glacial hollow was filled in the Quaternary period receiving its waters from a dozen or so mountain streams and rivers; the only emissary is the river Bardello. Inhabited since prehistoric times when it villages were built on stilts on the edge of the water, the abundance of fish and birds in the lake has been exploited for centuries.