In Roman age, Lake Como and Mezzola Lake were united. Only later, the debris from the numerous river Adda floods started to build up and eventually created the Pian di Spagna (Spain Plain) the two leaks kept being joined together by the final stretch of the Mera river. The paramount importance of this location is highlighted by the Ramsar Agreement, a fundamental international treaty for the safety of humid areas and their wildlife, Italy signed in 1971. Despite this, as a matter of fact, the way towards the creation of a protected haven has been extremely long and complex. The Pian di Spagna - Mezzola Lake Natural Reserve is a complex ecosystem featuring groves of reeds, humid meadows and farmland. Nonetheless, the real patrimony of this reserve is its avifauna, both nesting and migratory. Among the migratory species 200 different species have been observed on the site.