Separated from the banks of the Rio de la Plata by a road and pedestrian thoroughfare, the Chancery of the U.S. Embassy sits on a trapezoidal plot of land. The Brutalist building, designed by I.M. Pei with project architect Pershing Wong, is a three-story rectangular box on a one-story pedestal with a central atrium that rises from the entrance to the roof. The upper section is made of vertical, thin slabs of exposed, grey, reinforced concrete. The lower section, on the ground floor, has a smaller footprint than the upper section. Twelve thin steel and concrete columns are aligned with the perimeter of the upper section, giving the impression that the upper section floats atop the columns. The facades of the upper level are a grid pattern of square, recessed windows, each with a low, recessed sill delineated by a horizontal line of thin concrete.