RIOSECO, a partido, in the province of Valladolid, in Spain, the capital of which, of the same name, but with the prefix sometimes of Medina del, is a large city. There is a canal from it which unites the canal of Campo with that of Castille. It contains three churches, five monasteries, two hospitals, 1200 houses, and betwixt 8000 and 9000 inhabitants, who manufacture serges and some other woollen goods, and ribbons and other silk goods. There are two fairs held annually, which were places of vast resort, but had declined, till of late years they have revived, and are again become of great importance to the place. There is also a town of the same name in the district of Reynosa and province of Toro, in a mountainous part of the country.