Constantine District, North(opens in new tab)
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You'll find this one in the Janissary camp between the Fatih and Gul mosques. The easiest way in is through the south entrance, which will annoy the shit out of the sentries.
Ifnore them and clamber up the guard tower pointed out in the above image. You'll find the next fragment sitting on top of it.
This one's near the top of a minaret just northeast of the Fatih Mosque. Climb up to the second balcony to grab it.
This one's much easier to find, although you may end up having to fight a patrol or two of guards after you've grabbed it. It's sitting in plain sight in the courtyard of the Fatih Mosque.
Just southeast of the last Fragment is the northwestern edge of the Valens Aqueduct. Climb up to where the arrow's indicating to grab the next Fragment.
You'll find the next one a short jog southwest from the Fatih Mosque, at the very top of the nearby Assassin Den.
Keep heading southwest, and you'll see this building:
Climb up to its roof, and you'll find the next Fragment on top of this dome:
Head over to the little canal that divides the north and south districts. At its mouth, along the district's outer wall, you'll see the next Fragment. Hop up there and grab it.
This one's a little tricky; while it counts as part of the northern district's tally, the easiest way to grab it is to head across the canal into the southern district and find this zipline (see the map image below for reference):
Once you do, latch on and you'll grab the next Fragment as you're sliding down.
The next one's just under the lip of the Column of Marcian, on its southeastern face:
Constantine North's final Fragment is at the northern end of the Forum of the Ox, on the ruined column-thing shown below:
Next: Fragments 1-11 in the South Constantine District