In the south of Roma, by the triangle where one of the Romulus Lairs is, there is a chest and flag that I am missing on a raised cliff. The bridge to this cliff (from the nearby Borgia Tower) is out and cannot be jumped. It is also impossible to glide over and no way to climb up from the road.
How in the hell do I get to this part? Do I have to restart and do the Lair again to get there?