Lanca di Santa Marta, situated upstream the confluence between rivers Po and Banna, is an environment rich in amphibians and aquatic birds. The Reserve stretches up to the confluence of the stream Banna into the river Po: the stream, together with its several and small affluents, drains the rainwater of a large pre-hill area in the south-east, known as "Pianalto di Poirino". The stream Banna is characterized by summer minimum flows and floods which are sometimes violent in the most rainy seasons. In the surrounding countryside, intensely cultivated, the tree rows running along the course of the stream Banna work as ecological corridors linking the Reserve to environments rich in fauna, like Villastellone Park. The Reserve covers an area of 164 hectares.
Lanca di Santa Marta e della Confluenza del Banna Special Nature Reserve is safeguarded not only by the establishment law of River Po Park, but also according to the regional law no. 47 of 3rd April 1995 "Norme per la tutela dei biotopi", the Decision 85/338/CEE of 27th June 1985, and the Directive 92/43/CEE of 21st May 1992, since it has been considered as "ecological entity of great interest for the conservation of nature" and therefore subject to the environmental-landscape regulations according to law 8th August 1985, no. 431 and the European regulations, recognizing it as SCI – Site of Community Importance (code IT1110017).