You may not believe this, but as that the Casa Rosada was growing to its present dimensions, at the opposite end of the square the Cabildo of Buenos Aires was shrinking at about the same rate.
Generations of Argentinean schoolchildren had the image of the Cabildo as it was on the rainy May 25 of 1810 engraved in their memories: a plain two-story horizontal volume with a central clock tower and five bays of arches on either side. Yet, if you went to Plaza de Mayo, let's say after 1940, you'd see a similar building, but of much more vertical proportions and with not five but only two bays of arches on either side of the tower. How come?
Actually, before it began to shrink, the Cabildo had one last growing spurt. In 1880, the notable architect Pedro Benoit extended the tower by ten meters and resurfaced the whole building with Neo-Renaissance ornamentation. That would be a short-lived new glory. Less than a decade later the Cabildo would loose three bays on its north side to the opening of the grand Avenida de Mayo, the new main axis of Buenos Aires. It also lost its tower.
What was once a simple but proud public building had turned into undistinguished urban fabric. It narrowly survived several calls for its demolition and in the early 1930s lost another three bays, now to the south, to leave room for the newly opened Diagonal Sur. With this loss however, the building regained its symmetry. Calls were now for the restoration of the colonial building. In 1940 the architect Mario Buschiazzo, a pioneer of historic restoration, completed the reconstruction of the Cabildo, bringing back not only its plainer language but also its original clock tower, even if a tad shorter, to account for the new proportions of the building. And the Cabildo was now a historic monument.