The stronghold of Arquata del Tronto was heavily damaged by earthquakes in 2016 and it drew the attention of the experts in reinforcing historic buildings. They regarded it as a case study, a predicting model of the failure in employing specific construction elements in fortified architecture, whose geometric and material data were only approximately considered. The overhanging battlement is the most seriously damaged part of the building and has raised particular attention and interest. As often happens in other castles and fortresses, it dates back to the late 19 th and even more to the 20 th century. A first close examination of the building's repairs shows how the new additions, whose maintenance is difficult, ended in failure. The additions were inspired by ancient details, but nonetheless they are unreasonable from the point of view of structure and durability: they -and even more the irrational repairs of the last decades -are the principal cause of failure. Material decay -closely linked to circumstances and places -has also played a decisive role. An extensive and rigorous historical research is necessary to find the sources and to evaluate their nature and limits, as well as to relate all information to the building, thus operating in close correlation with the building archaeology, by now a so widespread and consolidated research field. . Jointly, the written documents and the building itself in its historical stratification allow a better analysis of the structural behaviour , an essential step to achieve an effective restoration planning.

Medieval archaeology has developed very effective instruments for investigating the smaller rural settlements and local production and construction techniques, on which the documentary sources are scarcely fluent. However, documents assure precise hints or general references to which archaeologists do not give up. In the same way, the most abundant, although indirect institutional sources, and the technical literature, from the Modern Age to the nineteenth century, are very useful to understand this kind of construction, with local materials and according to local models and practices -widespread in rural Europe until the early twentieth century. The historic villages of the upper Tronto Valley, near Ascoli Piceno, can offer a good example in a territory devastated by the 2016 earthquake in which material sources have been heavily depleted. The documents -although discontinuous -often explain constructive choices. The nineteenth-century literature describes the territory in a transformation phase, still based on the scarce local resources, and returns the mentality and the expectations of the contemporaries. Literature and documents contribute to consolidating the role of the built heritage as a historical source, highlighting both the cultural depth and the nature of housing resources that characterize the individual buildings and villages.