Reinforced concrete structures built without reference to a seismic design code in areas that have subsequently been included in a seismic zone may significantly increase the seismic risk of a country. At present, in Italy approximately 60 percent of the building stock, of which reinforced concrete buildings are a large fraction, belongs to sites not considered seismic originally. Furthermore, many reinforced concrete structures date back to the post-WWII period and are now at the end of their conventional life cycle, which could imply problems of degradation of the mechanical properties of their elements. Several of these buildings, at the same time, may be -or are already- considered part of the national cultural heritage. In this context, the case of the first reinforced concrete high-rise buildings, dating back to the 1950’s and reaching a height of 30 or more stories making use of normal strength concrete, is of particular interest. Such buildings are simultaneously in Europe and in North-America. Design was based on manual calculations, with an allowable stress approach without consideration of the ductility resources and, in the Italian case, without any requirement of seismic capacity. The design, however, is often based on very effective intuition in terms of structural concept. This point is well reflected in two high-rise buildings constructed in Milano, Italy, at that time: the Pirelli building and the Velasca tower. They present, and experimented at their times, two different structural schemes, both very effective with respect to seismic action: the Pirelli with a shear walls scheme, the Velasca tower with a tube-in-tube one. The latter is one of the first applications of the concept, which will have great development in the following years particularly in the USA. It is not by chance that the structural designer has been for both Arturo Danusso, who devoted his activity of young researcher to the beginnings of structural dynamics and in 1908, in the period following the Messina-Reggio Calabria earthquake, was involved in defining first requirements for developing resistance to horizontal actions for the reconstruction of the two cities. The re-analysis of the two high-rise buildings, performed with today’s computational means and with reference to present code requirements, presented and discussed in detail in this work, has shown high capacity resources and very effective behavior characteristics. As a conclusion, the seismic safety of existing high-rise buildings in reinforced concrete necessarily implies their re-analysis and the consideration of many different aspects related to the time of construction and to the effect of the period elapsed. Yet, from the structural point of view, these buildings, albeit designed with analysis tools not comparable to the present ones, are often found to reflect great wisdom and intuition in the structural concept.