This feat of arms was surpassed in the same year by a still greater event, the capture of Lisbon, the important city at the mouth of the Tagus, the future capital of Portugal, and the port from which the Portuguese ships were to sail forth on their voyages of discovery both to the east and the west. Affonso Henriques had long wished to capture this great city, for if he possessed it as well as Santarem, he would be able to defend the Tagus as his southern boundary, and have a much better base of operations. This ancient city was, from its position on the Tagus, the natural capital of the western coast of the Iberian peninsula, and had been an ancient Greek colony. The legend that it was founded by Ulysses, who gave its name, Ulyssipo, afterwards corrupted into Olisipo and Lisbon, is an ancient one; and it certainly held that name up to the time of Augustus, when a Roman colony was fixed there, and its name was changed to Felicitas Julia. Its capture by the Moors in 714 had marked one of their greatest stages of advance, and it remained the capital of their province of the Belatha for more than four hundred years. It had three times been captured by the Christians--in 792 by Alfonso the Chaste, of Castile; in 851 by Ordonho I., of Leon; and in 1093 by Alfonso VI., the father-in-law of Count Henry, but had only remained in their possession twenty years after the first recapture, and only a few months upon the second and third occasions. On this occasion Affonso hoped to be permanently successful, and to make it the capital of his kingdom.