Between roughly the 5th and 11th centuries, the Roman town of Circeii was abandoned by the local population, by then very small, who settled mainly along the slopes of the mountain in scattered, mostly makeshift dwellings that were less exposed to enemy attacks.
Although the Rocca had long been recognised as essential for defending the coast and as a safe landing place for sailors passing off the Tyrrhenian coast – so much so that it is mentioned as the Cove of the Arabs in the “Book of King Roger” compiled in 1154 by the Arab geographer al-Idrisi – it officially appears in papal records in the very first years of the 12th century, when Pope Paschal II (1099-1118) entrusted it to Hugh of Alatri, cardinal of the Twelve Apostles.
Medieval documents of the 11th and 12th centuries speak vaguely of “Rocca de Circegio”, “Rocca Circea”, “locus qui vocatur Circellu”, while the name Castrum Sancti Felicis appears for the first time only later, in 1259. In a deed of exchange of 1170 between the Frangipane, lords of Terracina, and Rainone of Tusculum, the territory of the Circeo begins to take shape and a small settlement can be made out in our town: besides the “Rocca de Circegio”, the deed mentions the “tenimentum S. Felicis cum insula”, a church with its appurtenances (the insulae).
The location of the Rocca remains uncertain, although recent studies suggest that in medieval times the stronghold stood on the highest point of the mountain, on the foundations of the ancient sacred place dedicated to Circe, a hypothesis supported by the discovery on site of early medieval remains.
However, a true fortified village or castrum was only built in the second half of the 13th century, when the Rocca and the mountain became part of the possessions of the Roman preceptory of Santa Maria on the Aventine, seat of the provincial master of the Knights Templar in Italy.
The Templars were present at the Circeo from after 1239 until 1259. They repopulated the old Roman town of Circeii, built the wonderful Tower that still dominates Piazza Vittorio Veneto with its bulk, and rebuilt the fortification walls on the Roman remains, turning the Roman town into a medieval castle that can still be read today.
The Templar wall encloses the Historic Centre on the west side, at Piazzale San Francesco, continues on the south side along Via Gino Rossi in continuity with the Cyclopean Walls of the 6th century BC, and in the north-east corner, near the garden of Vigna la Corte.
The stretch of medieval walls at Piazzale San Francesco, certainly the best preserved, had two hollow rectangular half-towers at regular intervals, still visible, beside which were the two original entrances to the medieval village, now blocked by infill and modern buildings. The corners of these towers are reinforced with well-squared limestone blocks. A short section of battlements is still visible, whose profile shows the original height, which looks rather modest today because the surrounding ground level has risen considerably.
The building technique is the same as that used for the Templar Tower: limestone blocks laid in irregular, wavy courses, alternating with courses of reused small bricks or fragments of marble slabs. This irregularity is not constant along the whole wall, but is especially typical of the northern and western sides, while on the eastern side, facing the sea, the courses are almost straight.