The Ribera del Duero in Castronuño is a nature reserve located in the province of Valladolid. It extends in the section of the Duero between Pollos, Castronuño and Toro. It is important for its aquatic birds, colonies of gray heron, martinete and little egret and other birds in danger of extinction. Tordesillas is interesting for its churches, convents, noble palaces, hospitals and restaurants. A must is the Royal Monastery of Santa Clara de Tordesillas, National Heritage, built in the 14th and 15th centuries. Toro is one of the historical and artistic landmarks of the area, with its famous Romanesque Collegiate Church, where the exhibition of "The Ages of Man" was held in 2016, The Romanesque church of Santa María del Castillo in Castronuño is located on a hill from which the entire Douro estuary is dominated. In Alaejos, the towers of its two churches of Santa María and San Pedro stand out. Chicken cheeses are famous.