Discover the Assassin's Tomb inside Santa Maria della Visitazione.
Assassin’s Tombs are available to you once you complete the memory ‘Novella’s Secret’ in DNA Sequence 4 (refer to “Undertaker” for more information). To locate a tomb, search the map for a icon. If you have not synchronized the view point in that area yet, it will not be revealed to you. You must also have completed through a certain DNA Sequence for them to appear.
You can unlock this as early as DNA Sequence 9. This memory is called ‘Visitazione's Secret’ and is located at the Santa Maria Della Vistazione church in Venice. You must first climb the church and make your way to the back corner near the tower. The skull “lever” will be at the base of the tower.
When you begin, you need to perform a leap of faith into a bale of hay. This will alert two guards sitting playing a card game. Assassinate the first guard and the second will run away. Chase him down and assassinate him before he alerts more guards. If he does, there are four more guards to take out. If not, just run forward and open the door. Opening the door will reveal a timed switch. When you pull it, the camera will pan to show you your path. Along the way there are four more switches that unlock a section of a door leading to your destination. This section might take a few tries as you may run out of time and there are some annoying jumps to perform as you progress.
When you finally reach the end and all four locks are open, the door will open for you to access the burial chamber. Walk in and open the sarcophagus to retrieve the seal. When you exit the church, the achievement will unlock.
That last section with the timed platforms and the sideways jumps took me forever to do. All I can say is that if you're struggling with the Advanced Wall Jumps, go into the bit of corridor before the switch and practice them without any pressure.
The key to the jumps is that as you're running up the wall, just before the apex of your jump, let go of all buttons, sticks and triggers, then just push and hold LS in the direction you want go, then finally right at the apex of the jump press A to jump.
I noticed a lot of guys on youtube having trouble with the sideways walljump . So did I at first until I figured out that the jump to the side ( left or right ) will always be a 90 degree jump from where you're facing . Don't worry about the bar to your right when you jump , face straight into wall , run up , at the apex , flick the stick to the right & hit jump ; you will automatically go to the bar & grab it . If you try to angle your character towards the bar you will fail , jumping into the water ! Also , don't rush , you'll have plenty of time ; there are only two wall jumps to do , at the start & the end .
Side note : Before you enter the big door , the room you're in has an alcove high up in a corner that requires a wall jump to reach . There's a wooden pallet leaning against a wall , jump up that to a wooden frame & wall jump to the bar above the archway for a treasure chest .
Quite tricky to find the route and you only get one preview of it! This also glitched on me when I grabbed one lever as time ran out and I completed all 4 but the floor didn't open! The secret to the wall jump (where you're holding a ring) is DO NOT HOLD the analogue stick - just press jump! If you thought the controls were bad here - try the Uplay bonus tomb!...Really, don't even bother - the controls are exposed as being retarded! 0/10
...Got this free with gold. Bad move by them as I always assumed the series was great, but the EMBARRASSINGLY retarded controls mean I'll never play these games again! Shame, great conceit/story/acting - dull gameplay and TERRIBLE clunky controls and stupid fixed camera in tombs! 7/10