Between 2003 and 2012, the New Bibliotheca Hertziana (Max-Planck Institute for the Art History) was built on the site of the garden of Federico Zuccari's sixteenth-century house in the historic urban fabric of Rome. The project aimed to demolish a 1960s building in the centre of Rome keeping its facades and constructing between them a more efficient, safer and more spacious building. The non-standard development of this conservation project led to the invention of several bespoke technical solutions and advanced conservation procedures. This innovative and bold construction process was developed by a pioneering engineering approach. The outcome of this experimental case study extends the building itself, having an impact on new developments in historical environments constrained by archaeological remains.Despite the foreign origin of the architect, the structural development of this building was entirely carried on by Italian engineers who relied on the ability of crafting the construction process as a unique case study. The structural engineers involved in this project were: Alberto Parducci, Alfredo Marimpietri, Marco Mezzi e Sergio Oliviero. Despite the ambition of the project, they were able to collaborate with the architect at the ‘technical design development’ stage, delivering a complete new structural design without interfering with the aesthetics of the scheme, which remained untouched.The archaeological and historical constraints, together with the complexity of demolishing and rebuilding in the centre of Rome, forced the engineers to adapt the idea of a post-tensed ribbed concrete bridge as a major building support for preserving the archaeological ruins scattered underneath the building. The structural invention allows the new building to fly over the ancient ruins without resting on the archaeological remains. This paper aims to retrospectively discuss the contribution of the structural engineers in delivering this challenging conservation project in central Rome, analysing how the new structural systems was developed, and how it was built. The ultimate aim is to disseminate an untold story, which can unlock the potential impact of this case study for similar constructions
