For defensive reasons Blera was built on a narrow tuff promontory, at the confluence of the Biedano and Rio Canale streams. The territory shows traces of human settlements since the final bronze age, that is, from the XII to the X century BC. , while Blera itself bears witness from the Villanovan era, that is, from the X to the VIII century.
In the archaic period (VI - V century) the population of Blera increased, due to the development of an urban center to which the agricultural agglomerations of the surrounding countryside belonged. The number of necropolises and burials attests to the importance assumed by Blera, which has become the urban center of aggregation of the nearby agricultural agglomerations spread over the territory, whose presence suggests that there has been a long period of peace, during which probably came to life a political-administrative center capable of designing a master plan for the necropolises.
In later times, that is, in the fourth century, the presence of fortified units suggests that with the decline of the powerful Caere peace was over, however the influence of Tarquinia, which replaced that of Caere, seems to have brought a tranquility which was not even disturbed by the Roman domination.
On the other hand, for its rich production of cereals, Etruria was useful for Rome itself, so it would have been foolish to bring devastation to its countryside. As for the connections already in the archaic era, the commercial routes from San Giuliano, Caere, Veio and Tarquinia arrived in Blera and then continued to Norchia and Tuscania, and to the north towards Orvieto. In the III century the Via Clodia was opened by the Romans, probably paving and rectifying a pre-existing Etruscan route.
With the fall of the Roman Empire the decline of the city began. Blera was among the first dioceses and had its own bishops from 47 to 1093. It was occupied by the Lombards of Liutprando in 739. In 772 it was destroyed for the first time by Desiderio, king of the Lombards, and a second time by Frederick II of Svevia.
After various events, in 1516 Pope Leo X gave it as a fief to Don Lorenzo from Anguillara. As Lorenzo's son died without heirs, Blera was administered directly by the papal state until 1870.