Nibby, Analisi, II, p. 511, wrote his note on the wall beyond San Francesco from memory. He says that one follows the monastery wall down, and then comes to a big reservoir. The monastery wall has only a few stones from the cyclopean wall in it, and they are set in among rubble, and are plainly a few pieces from the upper wall above the gate. The reservoir which he reaches is half a mile away across a depression several hundred feet deep, and there is no possible connection, for the reservoir is over on Colle San Martino, not on the hill of Præneste at all.
The postern or portella is just what one would expect near a corner of the wall, as a less important and smaller entrance to a terrace less wide than the main one above it, which had its big gates at west and east, the Porta San Francesco and the Porta del Cappuccini. The Porta San Francesco is proved old and famous by C.I.L., XIV, 3343, where supra viam is all that is necessary to designate the road from this gate. Again an antica via in Via dello Spregato (Not. d. Scavi, I (1885), p. 139, shows that inside this oldest cross wall there was a road part way along it, at least.)
The Cyclopean wall inside the Porta del Sole was laid bare in 1890, Not. d. Scavi, 7-8 (1890), p. 38.