The Adda Valley cuts through the high plains of Lombardy as an unexpected verdant hiatus. From the A4 highway or from the Milan-Venice railway, its appears for just a few seconds as a thick forest, steeply sloping down to the river, which is here particularly meandering. It is a passing view, sandwiched between the most monotonous Padania Classics landscapes, as defined by Filippo Minelli's photographic research, that is a haphazard accumulation of warehouses and homes, farms and international airports, with no discernible order or hierarchy. The creation of the Parco dell’Adda Nord, in 1983, certainly limited a further expansion of the urban sprawl towards the river.
Leonardo da Vinci considered this section of the valley as the most suitable background for its Virgin of the Rocks, “set” in the vicinities of local village Imbersago. Also, and more importantly, when Lombardy became resolutely industrial between the 19th and the early 20th century, this territory provided useful resources for the functioning of the productive machine. Today, the ancient hydroelectric power plants in Calusco and Porto di Cornate, alongside the famous Taccani power plant in Trezzo sull’Adda (Gaetano Moretti, 1906), interact with such heroic infrastructures as the two-storey, entirely metal San Michele bridge (Jules Röthlisberger, 1889), constituting one of the richest and most diverse industrial archeology ensembles of Northern Italy.
The nomination of Crespi d’Adda was the unexpected personal success of few enthusiasts who worked on the application dossier, in the first place the university students belonging to the “Centro Sociale Fratelli Marx”. At the same time, for Unesco this was a consistent choice in a trajectory of progressive diversification of the typologies of heritage protected by the association. In fact, in the mid-1990s, a broad interpretation of the notion was widely accepted. This also encompassed 19th and early 20th century architecture, previously overlooked even by preservation specialists, and typologies which were distant from traditional monuments. Besides its own qualities, Crespi d’Adda was also the right proposition at the right moment.