some of them travelling via Gibraltar. Gibraltar became Crown property again in 1501 at the order of Isabella and the following year it received a new set of royal arms, which is still used by modern Gibraltar, replacing those of Medina Sidonia. In the Royal Warrant accompanying the arms, Isabella highlighted Gibraltar's importance as "the key between these our kingdoms in the Eastern and Western Seas [the Mediterranean and Atlantic]". The metaphor was represented on the royal arms by a golden key hanging from the front gate of a battlemented fortress. The warrant charged all future Spanish monarchs to "hold and retain the said City for themselves and in their own possession; and that no alienation of it, nor any part of it, nor its jurisdiction ... shall ever be made from the Crown of Castile." At this point in history, "Gibraltar" meant not just the peninsula but the entire surrounding area including the land on which the towns of La Línea de la Concepción, San Roque, Los Barrios and Algeciras now stand. To the east, Gibraltar was bounded by the Guadiaro River, and its northern boundaries lay in the vicinity of Castellar de la Frontera, Jimena de la Frontera, Alcalá de los Gazules, Medina-Sidonia and Tarifa. From the 16th century, the modern meaning of the name came to be adopted – specifically referring only to the town of Gibraltar and the peninsula on which it stands. Under Spanish Crown rule, the town of Gibraltar fell into severe decline. The end of Muslim rule in Spain and the Christian capture of the southern ports considerably decreased the peninsula's strategic value. It derived some minor economic value from tuna-fishing and wine-producing industries but its usefulness as a fortress was now limited. It was effectively reduced to the status of an unremarkable stronghold on a rocky promontory and Marbella replaced it as the principal Spanish port in the region. Gibraltar's inhospitable terrain made it an unpopular place to live. To boost the population, convicts from the kingdom of Granada were offered the possibility of serving their sentence in the Gibraltar garrison as an alternative to prison. Despite its apparent unattractiveness, Juan Alfonso de Guzmán, third Duke of Medina Sidonia, nonetheless sought to regain control of the town. In September 1506, following Isabella's death, he laid siege in the expectation that the gates would quickly be opened to his forces. This did not