in's Creed 2 Help??!!?

Ok, In in's Creed 2 i'm at the point where I nee all 30 Codex Pages. Well, I have all 30 and I no so cause I can talk to Mario but he tells me to go to Leonardo. Problem is I can't find Leonardo for **** lol. I've looked for his icon in Venice and Florence adn I can't find his ***. Please help