Dungeons in Tuscany are located in the heart of the city.  To enter them you have to use the skull located in the eastern part of the building, in a narrow street. 
In the first room, move around the edges  and activate the switch. 
In the second one finish three soldiers.  Now look for the shelve with some barrels from which you will be able to jump on the beam and then on the platform. 
Jump right onto the beam that is under the wall made of timber.  Move to the right to get on the platform, then jump to the left on the next beam.  Now you can get to the elevator.
Use the stairs and grab the edge located above to jump down on the guard. Then get onto the chandelier  and catch the rope.  You will find yourself on the platform. Jump to the next part of the dungeon.
Opponents from the bottom can be lured and killed - they will not interfere with your plans.  At the top move right using logos.  When you will be above, finish some guards.
Run to the opposite part of the room and turn right - jump to the bridge.  Move up using a rope. 
When you will be in the center of the room, balancing on a rope, swing to the right and jump on the railing, to kill a soldier who will probably already notice you.  Before you will move further through the door, you can attempt to acquire the secret chest (containing 250 gold). Get to it using the handles above the doors on the second floor. 
Now get to the railings near the ceiling  and go to the opposite corner of the room.  From there, jump on a beam and land on the second floor. Then go through the door.
Time to climb on tower - jump on the next wooden stairs so that the archer won't be able to see you (the camera will show his movements).  Kill a soldier and ruse the ladder. More acrobatics moves will be necessary here - at some point you will be able to use handles. Climb using them when you will be sure that guards will not see you. 
Climb on the window to get to the handles on the left.  Then get on the beam and go to the other side. 
On the other side of the beam you will find another handles.  Use them and climb to room at the top. 
Take the treasure from the sarcophagus  and exit through the flap in the roof.