In 2000, RPBW was commissioned to expand the Morgan Library. The site did not allow extensions in the direction of the surrounding streets (Madison Avenue, 36th and 37th) but only in the space between the existing ones. Any intervention should therefore be carried out within the existing perimeter and must respect the historical pre-existence. It was then excavated (up to 17 meters deep) all around the buildings, to find in the subsoil the areas where to place the deposit for the collection and the Auditorium. In the space released on the surface, there were 3 pavilions that connect to the historic buildings, leaving a large "square" free for public functions. The square is the heart of the intervention, a place of rest and relationship and above all a point of distribution that facilitates the achievement of every wing of the Library. The new pavilions, the square and the three historic buildings are linked to each other by a transparent glass and steel cover.