The heart of Buenos Aires has always been the Plaza de Mayo.  On this famous square lies the Casa Rosada (Presidential Palace), the Cathedral and the Cabildo (Town Hall).  Built in 1748, this building has witnessed Argentine history since its earliest stages.  It served as house for the Government during the colonial period, and it was inside its walls where the first Junta gathered in 1810 to plot independence from Spain and to set up the first government of Argentina.  The structure today is only a portion of the original one which had 5 arches on each side of the tower instead of two.  The Cabildo has been declared a National Historic Monument and today serves as a National History Museum.