Many nuraghic monuments date to the 2nd and the 1st millennia B.C. Numerous nuraghes and nuraghic villages are rather well-preserved. Among the most important the following nuraghes should be mentioned: Is Tostoinis (called Taccu Addai by the people from Ussassai) and Perdu Isu. The first one was a settlement of rather considerable dimensions: in fact, there are about 40 nuraghes and huts, moreover there is a Giants' Tomb here. The second village consists of 11 nuraghes and huts. Besides, one can see here the presence of ancient cistern in a form of a well, probably used in the antiquity as a store for water. Other nuraghes had also their historic importance, these are: the nuraghic fortress of Sa Tumba, situated in the locality of Scaloni; Masu Matta that is behind of Gairo Taquisara; the nuraghe of Genna Didu - at the border with the territory of Tertenia; and a unique nuraghe of Su Serbissi, located on the highest peak of the mount of Serra Serbissi, overlying frontally the village of Taquisara. This nuraghe is so particular because it is connected to a vast cave underneath the nuraghe through a tunnel. The cave was formed in the rock of the dolomite mountain that crosses the mount from one side to another. Serra Serbissi and its homonymous nuraghe is situated at the border between Gairo and Osini, so the beginning of the cave is on the territory of Gairo, and its end - on the territory of Osini. Close to the crossroads Gairo Taquisara - Osini the nuraghe of Coccu is situated, which is the last one found recently on the whole interior mountain territory.
There are the nuraghes of Ulei, at the border with the territory of Lanusei, Musciu, Sa Perda de S'obiga, Nurcu, Genn'e Masoni, Sa Serra de is Perdas, located in Is Carcuris - at the border with the territory of Osini, Sa Brocca, Cuguddadas, Museddu, Is Follas e Perdu on the plain and on the coastal territory. Some of them belong to the Commune (municipality) of Cardedu since it has become autonomous. Nuraghic wells can be found in the locality of Taccu.
There is a castle in the locality of Perdu Pili, that once belonged to the marquisate La Rosa of the County of Quirra, which traces do not exist anymore. The Nuraghe Temple, situated in the place of Cuguddadas, is a very interesting monument, one of the most ancient and well-preserved monuments, but unfortunately not rather enhanced on Sardinia. It's also called Su Presoneddu (translated from Sard means “the prison”), because one can even nowadays find some underground rooms with iron rings fixed in the walls, that in the antiquity were used for detaining prisoners. The wedges of the small stones, used for its masonry, are of black stone deriving from the volcanic hill of Bari Sardo.
According to Alberto La Marmora and his work “The Itinerary of the Island of Sardinia”, once there was a nuraghe around the peak of Perda 'e Liana, but today there are no proves to support this affirmation. There are other nuraghes in Perdu Isu, Coili, Is Tostoinis, and Scala Accussa, in Taccu.
The nuraghic complex of Serbissi on the border with Osini is very important. It consists of several nuraghes located along a closed fence, under which there is a vast dolomite cave with 2 holes: one on the territory of Gairo, and the second - on that of Osini. Its position, dominating the profound pass of Genneùa, makes us think about a fortification, that in the past served to impede the access of those, who almost for 2 thousand years menaced the local population, to that point which was the obligatory passage to reach the inland from the coastal plains. Here it's probably referred to the Galillenses, that are still called the Barbaricini from Barbagia of Seulo. The remained toponym “Serbissi” (“servise”) confirms this presumed function of the nuraghe, which it continued to operate in the Middle Age as well, so that there was no necessity to built another castle with the mortared masonry.
The nuraghes are antique constructions that date back to the prehistorical period. The primary material used for their building was huge boulders and nothing else, not even lime to strengthen them. The boulders are put in decreasing circles in order to create the structures in form of truncated cone, sometimes reaching the height of 3 or 4-stored buildings and having basement diameter of even more than 10 meters. Their entrance usually looks on the east. Inside there were one or more ovoid rooms and/or cells, galleries and a winding staircase, that connected with possible lower or upper floors and a terrace. Outside they are sometimes surrounded by other constructions. As it has been mentioned above, these structures were built without any mortar: they were probably built at that time, when the technique of burning the limestone to get lime for fixing wasn't known yet. In some very rare cases when the building was realized with the use of some fixer, it was exclusively clay, and the boulders used were of more moderate dimensions than those of the nuraghes built without any fixer. The boulders for the construction have the same nature as those from the areas nearby, chosen for building the nuraghes: lava, granitic, basaltic, etc. They are bigger and rougher in the foundation than in the upper part, so that sometimes their dimensions exceed a cubic meter; as the boulders are put one upon the other their dimensions decrease, while the preciseness of the work increases, becoming more accurate and difficult. In spite of the asperity of every boulder's edges the structure itself has a rather regular form, with the boulders precisely aligned. There are some nuraghes, probably even more antique, which form differs from the typical form of truncated cone: their walls are almost vertical, while the basement and the roof are not round, but a bit elliptical. Almost always the entrance architrave is so low, that everyone who wants to pass through it to enter inside has to go on all fours or, in any case, bended. The inside rooms have an exclusively ovoid form and their diameter is of about two seconds of the basement diameter.
Some people sustain that there was a dome on the top of nuraghes. But if it really were so, it would be very difficult to reach the top and start the process of destruction, which is periodically performed by certain people, who ignore the damage, caused to historical and artistic culture, as well as to the economic aspect, deriving from a possible usage for touristic purposes. It is, actually, believed, that once there were thousands of such nuraghic constructions spread all over the island, sometimes more concentrated in some particular areas, while nowadays very few of them remained intact, or almost intact. The nuraghes can be found alone, isolated on a large territory, or attached to other ones, which, in turn, can be gathered in the way of an enclosure or surrounded by external constructions, or yet other ones of large dimensions, accompanied by smaller ones, physically attached and internally connected with them.
The scope of their construction is rather disputable, because it's difficult to find any historical, or even prehistorical, demonstration of their destination. Some people believe nuraghes were herdsmen's homes, others take them for fortresses or watchtowers. Someone assumes they served as tombs or religious temples, dedicated to the cult of gods or built in their honor, and someone considers them monuments built in honor of ancient victories. But the conducted studies have not revealed many elements yet, which could help to find in the nearest future any definite and certain answer to the mystery, that still today veils the remote past. However, the most credible affirmations sustain them to be structures, destined for a public use of thereof community. This supposition is based on simple observation of the facts: the enormous scale of works for building the nuraghes (huge and heavy boulders and incredible heights, restricted groups of people that were involved in their construction, considering that their use was probably limited to the familiar circle of people), makes it impossible, that the structures were destined only for a private use; besides the entrance gives on the east, and its dimensions are so small, that one cannot pass there on foot; the presence of various rooms and cells inside, possible pantries or closets where to store arms or religious tools; finally the presence of the staircase that led to the roof, an excellent watching point, or where to erect altars, which could be seen from distance or which could bring the nearest possibly to the sky- the seat of gods, or where to carry out magic rituals, or propitiatories, or religious ceremonies, probably relating to a possible antique cult of celestial bodies. All these corroborates the theory of a strategic value of the structures, in military or religious purpots, or even both. The typical geographical position of these antique constructions is in the places, that in the past had crucial importance from the military point of view: the position of the nuraghe of Serbissi, for example, which is dominating the pass of the present Gairo Taquisara, and makes us think of it as of a fortification, or a watching and alarm point, that served to impede the only access to the coastal plains from that point of those, who almost for 2 thousand years menaced the local population (probably, it's referred to the Galillenses, that became afterwards the so called Barbaricini from Barbagia of Seulo). The village of Perdu Isu also remembers a fortification on the guard of the pass to the valley of Rio Flumini de Tula for protection of the biggest and the most important village of Is Tostoinis.