In 1542 natives destroyed Buenos Aires, and the Spaniards there fled to Asunción. Thus the city became the center of a large Spanish colonial province comprising part of Brazil, present-day Paraguay and northeastern Argentina: the giant Province of the Indies. In 1603 Asunción was the seat of the First Synod of Asunción, which set guidelines for the evangelization of the natives in their lingua franca, Guaraní.