The national poem of Portugal, Luis De Camões' Os Lusíadas, dealing with Vasco Da Gama's 1497 voyage to India, was known to Tasso, who liked it -- indeed, he considered it his only 'competitor.' Os Lusíadas, which is probably a bit underrated outside Portugal, belongs to the phylum of the great Western Christian epic, from Dante to Milton and Blake, but it provides some insights that its 'colleagues' don't:
* It tells a sea adventure, unlike all others; for some reason, nobody, or at least no great poet ever wrote a poem on Columbus, although Tasso was quite sure someone would;
* It is substantially set in the present, unlike Ariosto's Orlando Furioso (eighth century) and Tasso's Jerusalem-poems (11th century); to be sure, Dante also set the Divine Comedy in his own days, but in places that he himself created;
* It is based on personal geographic and cultural experiences, as Camões actually knew India.
The historic(al) events of Vasco Da Gama's enterprise are simplified, but preserving their main dynamics. Although Da Gama is shown as nobler than he was, e.g. he never tortures prisoners in the poem, the "bloody" side of colonialism is not hidden at all -- the Renaissance was way less hypocritical than (so-called, self-proclaimed) "Enlightenment" politics and literature. What Camões shares with the other Renaissance geniuses is ambivalence as the epitome of the complexity of Reality: celebration and j'accuse, Christianity and pagan Classical Antiquity, virtue and eroticism, Nature's beauty and the horror of the Cross, heroism and irony, history and mythology, optimism and pessimism, Fortune and Providence, . . . At the same time, Vasco Da Gama is different from almost any other hero, because -- like Aeneas -- he acts on behalf of others, for a purpose that he did not choose; his glory coincides with his obedience, unlike Achilles, Odysseus, Ariosto's Ruggiero, Tasso's Rinaldo/Riccardo, whose deeds also accomplish a general purpose, but, say, indirectly, as a side effect.
A very interesting subject, linking Camões to Milton, is that of Paradise. Like all his contemporaries, the Portuguese poet identified, at least on a literarily level, the Biblical Eden with the islands in the Atlantic Ocean, especially the Canaries, plus India in the Far East, in this case. So, thanks to the Lusiads, readers reach a "widespread" Paradise that the Westerners had lost: they now regain it, and even commercialize it. It would like to seem the beginning of a New Era, but what it actually entails is the definitive loss of Eden. In fact, one century later, Milton will say that the mountain of Paradise had been destroyed quite early by the Flood. This, on the other hand, will give rise, in literature and movie, to the attempt to discover it somewhere else in the universe, see CS Lewis' Space Trilogy and James Cameron's Avatar in his wake.
For a very good Italian version: Lusiadi, transl. by Mercedes La Valle, Parma: Ugo Guanda Editore, 1965.