The Pirámide de Mayo is the oldest monument in Buenos Aires. It's construction was ordered in 1811 to celebrate the one year anniversary of Argentina's independence from Spain. The monument is topped by a sculpture of liberty done by French sculptor Joseph Dubourdieu. While a center of all things political in Buenos Aires, Plaza de Mayo is rather small and unkempt, save for this small but elegant monument.

http://en.wikipedia.org/wiki/Pir%C3%A1mide_de_Mayo.