During the 10th century, the descendants of Count Guifré extended the borders beyond the frontier that had been established during the Frankish campaign. The new lands, controlled by means of a dense network of castles, were known as the March. In the area of El Penedès, a land of considerable geostrategic importance, the castle at Olèrdola developed into a veritable frontier city. By the end of the 10th century, the border of the county of Barcelona had shifted to the Gaià River and remained stable until the conquest of Tarragona in 1118.