Valladolid Natural Spaces
Riberas de Castronuño
The Riberas de Castronuño is a natural space situated in the Midwestern region of the province of Valladolid, and covers the stretch of the river Duero between the localities of Tordesillas and Castronuño. The latter also contains the Embalse de San José (reservoir). The Riberas de Castronuño constitutes a classic marsh ecosystem, noted for its importance as a nesting and hibernating zone for many water birds. An interesting riverbank forest, formed mainly of black poplars, willows, white poplars, ash trees and hawthorns, accompanies the river along its course down the sedimentary plain.
As well as adding beauty to the plain landscape, this rocky area provides protection and refuge for a great number of birds, most notably, significant colonies of grey heron, night heron and little egret.
Castronuño is also a hibernating zone for a great number of mallards, shovelers, pochards and cormorants. Upstream from Castronuño, we find the interesting town of Tordesillas, site of many convents, churches, palaces and hospitals. The town gives it name to the famous treaty signed there at the end of the 15th century, by which the kingdoms of Castille and Portugal divided up dominion of the whole world .