Get to the prison | Chapter 3 - Florence, Italy Secret Files 3 Guide

Return to the ground (on the cart) and head to the prison (left).

Use the sword and cut the line which ties three barrels to the right of the building. A guard will appear after the barrels damage the window - he will left the door open. Nina can get inside now where she'll see interrogation of An-Nasir. She'll also eavesdrop on guards' conversation.