User blog comment:Jasca Ducato/Assassin's Creed: Revelations (360) - Official Assassin's Creed Wiki Review/@comment-673285-20111206223537

I'd just like to point out that Secret Locations are indeed in the game - they're simply more fitted into the plot, as opposed to being entirely optional. Most of them are anyway - I believe there are two (including the Vlad the Impaler's Prison) that stand as optional, and actually located in the Secret Locations section of DNA in the pause menu. The other 2-3 or so are integrated into the storyline.