The Pirámide de Mayo ("May Pyramid"), located in the center of the Plaza de Mayo, is the oldest national monument in Buenos Aires. Its construction was ordered in 1811 by the Primera Junta to celebrate the first anniversary of the May Revolution. It was renovated in 1856, under the direction of Prilidiano Pueyrredón. In 1912, after having undergone numerous modifications, it was moved 63 meters to the east, with the idea that a much larger monument would eventually be constructed around it.

The monument is crowned by an allegory of Liberty, the work of the French sculptor Joseph Dubourdieu. From the ground to the peak of the statue's Phrygian cap, the Pyramid measures 18.76 meters.