Plaza de Mayo is the oldest square of Buenos Aires where it took place of the most important historical events of Argentina. The name is due to the tribute of the 25 of May 1810 revolution, which tool place at the square. Around the square, you will find a lot of governmental and historical buildings like Cabildo, Metropolitan Cathedral, The Pink house, Banks and many more. Under the square, you will find the subway "A" which has connections to Subway "D" and "E".
In the centre of the square, there is a pyramid called "Pirámide de Mayo" which was built in 1811 to celebrate the centenary of the revolution and it was reformed in 1856 by the artist and architect Prilidiano Pueyrredón. Between the pyramid and the pink house, there is a monument of Manuel Belgrano, the creator of the national flag.
You will find many office workers that cross the square on weekdays walking fast and agitatedly. You will also find school buses with kids that came to visit historical buildings like the Cabildo. Some days you could also find protests against goverment measures, don't be scare since you can buy cheap choripanes at protests.