After exiting the small lake of Olginate, the Adda River takes a winding course and forms a meander whose bend, facing west, marks the boundary of a marshy area called Isola della Torre and Isolone del Serraglio, located in the municipality of Brivio. It is easy to reach, as it is located along the state road S.S. Nr. 639, in the middle section between Calolziocorte and Cisano Bergamasco. The morphology of the territory is typically fluvial as it is characterised by abundant alluvial deposits that have determined its flat aspect. From an environmental point of view, this area is extremely interesting because it has no human settlements, whether industrial or agricultural, yet is biologically rich.