In Assassin's Creed Revelations, which legendary explorer's memories does Ezio seek in Masyaf?

In Assassin's Creed Revelations, Ezio seeks Altaïr Ibn-La'Ahad's memories in Masyaf.

The game brings together the two protagonists of the earlier games: Ezio, now an older Assassin, and Altaïr, whose life was explored in the original Assassin's Creed. Ezio travels to Masyaf to locate keys that reveal Altaïr's memories and the secrets stored by the Brotherhood.

The main modern and historical setting is Constantinople, called Istanbul today, during the early sixteenth century. Ezio's investigation connects the Ottoman city, the Masyaf fortress, and the long history of the Assassin order.

Altaïr is not an explorer in the usual geographic sense; he is a Syrian Assassin and mentor whose career reshapes the Brotherhood. The question's “legendary explorer” wording refers to Ezio's search for his predecessor's recorded memories, not a real-world exploration voyage.