Region
Prison Tower map
A tower inside the streets
Prison Tower is not its own top-level region in the nine-area list. It sits inside Paris Streets. The fast-travel list still gives it a Mirror of Life. Named pieces are Guard Level, the Roof of the Tower, the Prison Tower Lift, and Warrior's Crane.
Joan's first fight, The Warrior, is on the roof. The sage sigil associated with her is nearby and does not need a traversal skill. The chapter page has the approach from the sewers. This page is the short index for when you are already in the district.
What not to expect
There is no separate pin pack for this tower in the sources beyond those room names. If you need the Burned District or the Court of Miracles, use the Streets of Paris map. They are neighbors, not floors of the tower.
What I ran into
This could have been three sentences on the streets page. I gave it a URL because people search the tower by name after the lift kills them, and sending them through the whole Paris chapter is rude.
Questions
Is Prison Tower a separate region?
No. It is a sub-area of Paris Streets with its own mirror.
Who is on the roof?
Joan of Arc, fought first as The Warrior.