Passetto di Borgo

Italian Wikipedia dates the corridor's formation to 1277, under Nicholas III, inside a stretch of the Vatican walls, and records its use as an escape route by Alexander VI in 1494 and by Clement VII in 1527. Roma Capitale's Castel Sant'Angelo page describes it as a raised, fortified passage connecting the Vatican with Castel Sant'Angelo, running over the Vatican walls. The corridor's western end lies inside Vatican City, and this guide does not say where along its length the border crosses. That is not caution for its own sake: the Lateran Treaty fixes the border only by an annexed map at 1:5000, with no verbal description at all, and the border commission of 1932–33 never had its conclusions ratified. No length is published here either, and no visiting information: no source states them.