Casa Rosada

In front of you is the seat of the Argentine government. Before you take in the colour, think about what lies underneath: this is where the defence of Buenos Aires began.

1First there was a fort

In 1594 governor Fernando Ortiz de Zárate began building, on this spot, then right at the river's edge, the «Royal Fortress of Don Juan Baltasar of Austria». Rebuilt in 1713, it became the Castle of Saint Michael the Archangel, home to governors and viceroys. In the mid-19th century much of the fort was torn down, and behind this building, where the Bicentennial Museum is today, Edward Taylor put up the New Customs House.

2Two buildings and an arch

What you see wasn't designed in one go. Francesco Tamburini joined the Post Office building and the old government house with the great central arch, begun in 1886. The whole complex was officially opened in 1898, during Julio Argentino Roca's second presidency. Look closely where the side mouldings meet the arch and you'll spot a slight asymmetry: the arch hides a difference in height between the two original buildings.

3Why pink?

The building was painted pink during Domingo F. Sarmiento's presidency. People often say the colour blends Federalist red and Unitarian white as a gesture of reconciliation; historians find that unlikely. What is known is that in the 19th century a paint made of lime and cattle blood was common: it gave this shade and protected walls from damp.

In 1955, military aircraft opposed to Perón bombed this building and the square behind you.

4What to look for

• The central arch and the small asymmetry where it meets the wings.
• The balconies overlooking the square, stage of famous speeches.
• The grenadiers of the guard, wearing the uniform of the regiment founded by San Martín.