We will start with this first mission, but we will take a break from the story for a good while, hitting both assassin tombs. Also, don't buy anything if you can help it.
Quick note about district 3, it's in carnival mode, and most of the people here are loaded, so pickpocket away for easy coin, just watch for guards.
Knowledge is Power
Just enter Da Vinci's house to start this. Which dechipers any codexes you have.
Climb over the south wall of vines to reach the dock. You can move on the dock to get in range of each.
Select your pistol and you have to hold the fire button until the beam is straight. This beam represents accuracy, so if you hold it for a moment and fire you could miss, but so long as you wait for the beam to become whole it is always a hit.
Return for completion, your mask, and a design on your cape.
Codex Page 14
This is in the newly-opened southern district, and directly south of Da Vinci's home.
This bell tower is just west of the carnival square. Careful, only the second VP ever to not have the hay directly in front of it. You have to jump north.
With these unlocked, let's get them in order.
Northwest - On the Santa Maria Dei Carmini, an incomplete church. One of the shortest VP climbs ever.
West - Just a bell tower.
South - This is very near the assissin tomb marker, it's the Della Visitazione, a somewhat small church tower climb to the cross. Jump east, may not dive but you'll land in the hay either way.
Southeast - A bell tower, climb the corner.
18. Head to the dance grounds where you shot up that one dude. The feather is on the west side of the north building.
19. West of here is another festive area looking to the south sea. Look up to the west building face for this feather up high.
20. To the west of here still is a ship on the water by the travel station. Climb up the mast and grab it.
21. Just north of the ship is a canal bridge. On the east side, climb up and behind the north building for this one.
22. The highlighted area in the middle of this district is the main festival grounds. East of it and on the boards over the streets is this feather.
23. To the west of these grounds is a canal. Going up the canal, above it, is this feather.
24. Just to the west of this canal is another one. The feather is near the bridge, up above.
25. To the very west of the district, this is over the north side.
26. Come to the north border where the little plateau is in the border on the map. The feather is above the street in the NE corner of this shape.
This tomb is in the carnival district, at the Santa Maria Della Visitazione. Enter via the button on the west side of where the tower touches the church roof.
Jump down into the hay. Kill the guard at the first chance, meaning you'll have to exit the hay and get him in the back, or do it quickly when he's turned to the hay.
Then it's a chase of the other guy. Easy to not lock on and just follow the second path, because he will always close a gate, so be ready to turn at all times. This is a much easier chase than before, and yes, he does stop to allow you time to catch up.
When he gets friends, just go up the right side of the door, and kill one-two of them in a leaping kill. Then counter kill the two guards, and quickstep behind the armored guy to kill him. Loot all their bodies for munitions.
*EASTER EGG: Activate the crank and then look into the water by standing on the edge of the surface so Ezio leans over. Just stay there for a while until you see it appear in a quick scene. Turn the crank again and look into the water and it makes one final appearance. Or search "Octi the giant octopus" on youtube.*
This next timed jump puzzle is a beast. The red sliders on the walls let you know time is short. And also, be ready to learn the advanced jump, which means just go up a wall and jump in a direction, such as right for the first one.
Also know that there are poles that help unlock the gate, and those are what you are being timed on, hitting all four of those. Your progress at these swinging poles stays, and if you fall early, feel free to re-use the crank to start the timer over. You have enough time to fall off once, so long as you know how to get back up quickly.
*NOTE: To swing, press the swing button and up. Just holding the swing button doesn't work.*
To start, run up the upward extended rock pillars to the left wall. Run up the wall and jump right to swing, then get to the next rock platform. From here, run up the right wall piece and jump left to swing to the next wall.
Then swing to the opposite wall, then swing up and around the statue. At the dead-end, wall jump left. Run around and jump to the pillar in the middle of a rock wall to reach the pole, get over, and quickly hit the fourth lever.
Drop down and head in for four chests and the tomb. Then the sewer path to get out.
San Marco's Secret
Now we head back to the previous district to the east for the final tomb at the Palazzo Ducale. It's not inside the locked portion, it's actually on the west side of the roof, where you entered with Antonio earlier. Find that spot in the NW corner of the building and follow the platforms to the top. Then take the roof west and drop down where you see the ladder and the button is on the left wall.
Safely drop down to the floor, then up to start the puzzle. Start with the east trial.
East Trial - Run to the east wall and up the right side to start on the path. Jump over the wall painting and go right, then left. Look over to the things that point up on top of the archway, and hop over all of them and the middle cross to get over. Climb up to the ledge of the bars, then go left and climb up the rail. Climb up the middle or sides of the organ, then jump to the lever hanging nearby to win. Hop back to the organ to get down.
North Trial - Hop the fence and run right to go up the white-ish column and climb up. Jump to the middle wall, then carefully hop the pegs in the wooden thing to the platform. Now jump to the right ledge and shimmy until you see the white pegs on the front and climb them up. Just run the left, up the rings on the wall, jump back to the board, and then to the lever.
West Trial - Run left then west, and climb up to the portraits on the wall to get on the structures. Hop west to the ledges and follow this first ledge to reach the boards in the corner, then follow the sticking out boards to the other wall. Up the ring and then climb up the window, hop to the pole, and swing to the lever (hold the direction of the second pole to swing). Jump to the cross thing, and when you fall grasp the bottom of it to get down safely.
South Trial - Run straight to the south wall and on either side is a cabinet to climb up, then to a ledge, and then to the stone platform. Then hop to the thin wall and go to the west wall. Follow the path to the second level. Go to the left side of this column and hop over the crosses, you can move on them, and then hop the wall boards on the other walkway to reach the south walkway. Then just up the window to about the mid-way point and jump to hit the lever.
With all four completed, jump down the opened hole for three chests and the final seal. Use the wall to exit.
Before we do so, turn in your one codex to Leonardo.
With all six seals, turn them into the chamber below the villa, using the wall in Mario's room, and you will be wearing Altair's armor, a huge boost in functionality and visual appeal.
However, since we most likely skipped the Missaglias armor set, getting that set still counts toward 100% completion. So hopefully with all that extra money you can get those pieces, all but one at least which isn't available. And be sure to only buy them in this town, because they equip, and Altair's armor is better. It appears in a wing in your house when you buy the other armor. Same with weapons in you have his sword now.
But do buy Altair's Sword from the blacksmith in town.
And a quick recap: we have 28/30 codexes, all but one armor piece, should have roughly half of the weapons from the local blacksmith, no feathers, no statues, and a few of the portraits.
Now is a good time to inform you of the portraits in the attic of the house, which is reached via your mom's room; two chests in there too.