Quote:The wall walk was protected by a parapet and merlons, both of which were about four courses high. Most of the merlons have been restored, but the forked ones of the type known as ghibelline on the fortified enclosure of the Rivellino, and perhaps also those of tower T12, may be original. The origin and significance of ghibelline merlons is obscure. They were common from the 13th century. Their occurrence on fortifications either built by the papacy or its supporters shows that they did not accurately reflect political loyalties. [The castle was the seat of the Roman-apppointed podestà in the 13th century - PDH]. The ghibelline merlons on the fortified enclosure of the Rivellino have stone hooks in the middle of them. These supported wooden flaps or shutters which protected the embrasures between the merlons. Elsewhere, such as on T12, the merlons have pairs of stone hooks which served the same purpose. The merlons on the later W. part of the Rivellino enclosure have slits in them, as do some of those on the walls on the N. side of the town. Crenellations retained these features right until the end of the Middle Ages. The few surviving merlons on the porta Bove at Viterbo, and many of those on the E. side of that town, all of which were restored in the mid-15th century (Ciampi 1872, 66), have slits with pairs of hooks above them. At the bottom of the parapet on the Rivellino, there is a row of beam holes which pass through its entire thickness. Such holes are an almost universal feature of the parapets of the medieval fortifications of Lazio. It is difficult to know just how they were used. They might have been for the attachment of wooden hoarding projecting' from the battlements to provide a vantage point from which the botto m of the wall could be defended; or else beams inserted into them may have supported a platform which served to widen the wall walk. This would otherwise have only been about 0.60-1.20 m wide, quite sufficient to walk along, .but hardly enough to perform any complicated manoeuvres. 

Quote:One remarkable aspect of this rebuilding is that it was all entrusted to masons from Lombardy. Itinerant Lombard masons and other craftsmen were to be found throughout Italy at all periods in the Middle Ages. However, in the 15th century a great many of them emigrated to the Papal State. Quite when this process began seems not to have been established, but by the 1440s they were already present in large numbers. There seems to be no single obvious explanation for this migration. Unemployment in the mountain villages from which they came must have been a strong incentive to emigrate, just as it is today. Warfare in N. Italy might have driven them from their ho mes, and created unfavourable econo mic conditions (Battisti 1959, 434), so that the Papal State offered attractive prospects in comparison. The presence of Lombards at Ro me in this period working in the service of the popes on the Vatican palaces and other building projects is well-known (Muntz 1879, 104, 232; Bertolotti 1881; Battisti 1959). They were also to be found in the smallest villages of Lazio. At Vitorchiano, Lombards are recorded working as weavers, barbers and hosiers (Aleandri 1911). Many settled, bought property, intermarried and became integrated in the co mmunity. Others, however, maintained close links with their homes in the north, returning periodically as did Guido and Ambroxino da Varese. The way they do minated the local building crafts at towns like Tuscania, establishing a virtual monopoly, suggests that they were in possession of skills not to be found locally. This is corroborated by the explicit statement in the Consigli for 1455 (I, f. 256v) that there was a shortage of building workers (quia in hac civitate est maxima penuria carpentariorum et latomorum), leading to the proposal that the payment required from foreigners by the statutes of the arte of the masons and carpenters be waived, since crafts men were being discouraged from coming to work in the town. Similarly, at Viterbo, the 1469 statute of the maestri di Pietra offered a two-year exemption from all taxation to foreign workers Ad reparationem civitatis Viterbii quae propter guerrarum discrimina, artificibus magistrisque utilibus destituta... (Egidi 1962).

These Lombards often worked on military architecture, including, for instance, the walls of Viterbo (Ciampi 1872, 72, 77), many fortifications belonging to the republic of Siena (Cecchini 1959), and Castel Nuovo in Naples. They even built the defences of the Kremlin for Ivan II of Russia. There can be no doubt that they had a considerable influence on building practice in C. Italy, being partially responsible in Lazio for the change to using [poor-quality mortared] rubble instead of ashlar masonry, and the re-introduction of brick manufacture and construction.  Their presence coincides roughly with the appearance of round towers in large numbers, and it is tempting to think they may have been responsible for the diffusion of this type of tower which had hitherto been less common in this area than in N. Italy and N. Europe. In Lazio, the earliest round towers—with the exception of one on the walls or Rome built possibly in the 12th century, and some isolated ones in the Ro man Campagna of uncertain date—are probably those of the walls of Rieti (Colasanti 1910) and the castle at Ponte della Badia (Serafini 1920), which date from the second half of the 13th century. These are virtually the only surviving examples of such towers built before the 15th century. Just when the late type of round tower first appears is uncertain. In Umbria, a round tower at Petrignano di Assisi was probably built by Nicola da Como in 1415 (Brizi 1895, 6). If it had a battered base, it is now buried by the rise in ground level outside the town. A very fine round tower with a batter and roll moulding at Corneto-Tarquinia near S. Maria di Castello was built in the 1430s (Polidori 1977, 235) , possibly on the initiative of Cardinal Vitelleschi, who had been secretary to Tartaglia. At Sermoneta to the S. of Rome, round towers were built c. 1448-50 by Onorato Caetani. In 1453, Michele di Prato wrote to Onorato telling him how he had described to Nicholas V the fortifications at Sermoneta: dissigli delle mura faceva la S.V. di nuovo et maxime del grossissimo muro e degli torriciellj tondj et scarpatj, a exemplo di quegli che a fatti la S. ta Sua (Caetani 1927, I, part 2, p. 88). Although Nicholas V built round towers at Castel S. Angelo and the Vatican, and may have been influential in popularizing towers of this type, it is curious that at the Campidoglio and on the walls of Rome he built or rebuilt square towers that are remarkably primitive-looking, and do not even have loopholes (Muntz 1879, 147-50, 158-60). Three round towers survive on the walls of V iterbo. One was probably built in the 1450s, and another in 1473 (Ciampi 1872, 66, 106). A good illustration of the respect accorded to the round tower is a large one at Nepi which in fact encases an earlier square one. It bears the arms of Calixtus II (1455-58).