"Il Bottaccio della Visona" (Province of Lucca, Commune of Capannori) and the "Bosco di Tanali" (Tanali Wood), situated in the western sector of the old bed of Lake Bientina, are the last two tiny residual strips of lowland plain woods that once surrounded the lake.

"Il Bottaccio" in the proper sense, with a surface area of about 20 hectares (but the whole Natural Protected Area of Local Interested covers an area of 46 hectares), falls totally within the artificial flood plain of the Rio Visona of Castelvecchio, which ends its course there.

The practically pollutant free waters which flow from the Pisan Mountains and run within the river banks, remain in the "Il Bottaccio", at least for as long as the marked regime of the Rio Visona allows, so creating marsh and semi-marshland habitats which gradually extend into woodland.

This is therefore an artificial habitat, but one still with strong natural characteristics. The geology is the same as that of Bientina Lake. In particular, "Il Bottaccio", situated at the foot of Castelvecchio Plain alluvial fan, corresponds to the old mouth of the Rio Visona.

The resulting soils, developed from alluvial deposits, range from gravel-sand and clay deposits; pedogenesis was disturbed by recurrent overflows.

The much varied landscape can be divided into four distinct types: woodland, wet meadows, reed thickets and the "ponds", all competing to form a varied mosaic.