Conservation is a complex concept having experienced a very diverse understanding in different historical periods and cultures. In ancient times, despite the singularities related to conservation, the interventions on historical buildings were basically aimed at safeguarding the spiritual or economic value of the construction, according to the current time standpoint. During the 15th and 16th centuries, although following the old style of classic architecture, conservation of built heritage was carried in agreement of the new architectural style. Regarding ancient monuments, the architects mostly involved in conservation were Giuseppe Camporesi, Raffaele Stern and Giuseppe Valadier. Accordingly, Ludovic Vitet, French General Inspector of Historical Monuments and pioneer of stylistic restoration, suggested that the interventions on monuments should be based on a deep knowledge of the original style to propose mimetic solutions grounded on evidences rather than hypotheses. Despite the principles of the Athens Charter, monuments were stabilized, repaired or even reconstructed with no scientific or historical insight.