Cosseria is a small agricultural commune on the northern slope of the Ligurian Apennines, sitting on the ridge between the upper valleys of the two Bormidas rivers. The territory is sparsely settled, with the economy based on vegetables and cattle.
The village has medieval roots: it is mentioned in a diploma of Otto I in 967, and was held successively by the Marchesi di Clavesana and the Del Carretto family. The ruins of a medieval castle — the Castrum Crucis Ferrae — still stand at the Montecala pass, with the original entrance gate, sections of the walls, and part of the keep surviving. The parish church of the Immacolata, rebuilt in 1656–60 and restored in 1831, has a fine rose window.