Today, we can still admire buildings and monumental works from the past. Merit is due to the simple, natural, healthy and essential raw material: lime. Today lime represents the binder for construction of the third millennium, with the “freshness” and “ability to surprise” that only an extraordinary material can boast, after centuries of hard and tireless work. Experimental data and scientific research identify in lime the only really compatible material with the majority of the works built by man from antiquity to the early twentieth century. With this awareness it is evident to all that, especially in restoration, the use of lime is most often the only choice. The use of lime is therefore the logical consequence of a process of substitution and integration of a pre-existing material, which should guide every good project.