Cagayan was one of the early "provincia"s that existed during the Spanish Colonial Period. Called "La Provincia de Cagayan", its borders essentially covered the entire Cagayan Valley, which included the present provinces of Isabela, Quirino, Nueva Vizcaya, Batanes and portions of Kalinga and Apayao. The former capital was Nueva Segovia, which also served as the seat of the Diocese of Nueva Segovia. Today, only remain of the former vastness of the province. The entire region, however, is still referred to as Cagayan Valley.