The operative complexities involved in the conservation of the archaeological heritage diffused across Italy’s national territory have long overshadowed efforts to mitigate seismic risk. Archaeological ruins appear as fragmentary structures, reduced to wall fragments. The gradual deterioration of materials and construction components and the anthropic transformations, permanently alters the structural integrity of these remains, rending them particularly vulnerable, determining worrying risk scenarios even in areas with low seismic hazard. Quantifying structural vulnerability requires the understanding of the relationship between the stratifications and transformations, the material and conservative characters, and the current structural behavior of the elevations. This paper presents a qualitative–quantitative assessment method developed as part of doctoral research in History Design and Restoration of Architecture at the Sapienza University of Rome. The method aims to overcome the limitations of a rapid analysis that sometimes disregards an understanding of the mechanical behavior and the historical-constructive history of the pre-existence. A reading system for structural ‘morpho-types’ proposed considers the ruin both as a structure (as a resistant system) and as a constructive morphology (an organism defined by the assemblage of materials in a specific form). The observation of some monuments of the Roman Forum enabled the identification of the key parameters influencing structural vulnerability and the potential collapse mechanisms. Additionally, the vulnerability is affected by factors that are not easily discernible through visual inspection alone, such as historical construction techniques and the impact of past conservation interventions. The model incorporates specific vulnerability indicators able to record aspects like the effectiveness of previous restorations, the reliability of connections, and the regularity of construction—elements that are “quantifiable” only through a careful and informed process of analysis.