31. The exterior of the Porta Maggiore, with the _specus_ over it, the lower one the Claudia, the upper one the Anio Novus. (The inscription of A.D. 404 is given in 1872.) Under these, but still on the top of the wall, the _specus_ of the Aqua Felice may be seen, built as usual of rough stone concrete. To the right or north of this may be seen the three _specus_ of the Marcia, Tepula, and Julia, passing through the wall in the opposite direction, now under the Felice, and originally under the Claudia and Anio Novus. These three _specus_ are carried upon one of the piers of the Marcian arcade, built into the great wall. Just beyond these, further to the right, is part of the last tower of the Claudian arcade. 32. The Porta Maggiore, with the _specus_ on it, seen sideways, and the north side of the Baker’s tomb. The last tower and _piscina_ of the Aqua Claudia; it stands at an angle of the wall projecting from it, and shews clearly that it stood there when the wall was built by Aurelian, and then incorporated into it. When the fortifications of Honorius at this gate were destroyed in 1833, the inscription relating to the aqueduct was preserved and built up to the right or south of the gate (shewn in 1872). Within the wall, behind the tower, is a large reservoir or _castellum aquæ_, of which there are slight remains, shewn in 967 and 968. A panoramic view of the line of the Claudian arcade, on the north side of the Sessorian gardens, taken from the extreme end of them at the west, is shewn in Nos. 542 and 543. On the left hand is the beginning of the arches of Nero, going across the foss towards the Cœlian; then the Porta Maggiore is seen sideways, with the two _specus_ on the top of it. Under this is part of one of the two great reservoirs believed to have been the Gemelli of Frontinus. Then comes the western wall of the Sessorian gardens, rebuilt by S. Helena, the construction being of the time of Constantine. To the extreme right is the ruin of the Basilica or Great Hall of the Sessorian Palace, repaired by him. This is miscalled a temple of Venus and Cupid on some of the maps. Having thus traced the Aqua Claudia from its sources into Rome, we must now do the same for THE ANIO NOVUS, which in its early part is distinct from it, as we have said. 1514. Sources of the Anio Novus above Subiaco. The river Anio in the highest point, with which the aqueducts are connected, is seen winding through a gorge in the rocky mountain, with remains of the bars or dams, across the river, forming the two upper lakes or lochs. The celebrated monasteries of S. Scholastica and S. Benedict are visible on the hill to the left. 1515. The River Anio, a little lower down, with remains of the second barrage or dam across it, forming the third loch or lake, with the modern bridge built upon the ruins of the old wall that formed the bar. Chapels of the monks of S. Benedict are visible on the hill to the right.