The Palace of the National Congress is the building built to house the National Congress of Brazil, inaugurated in 1960. It was conceived by the architect Oscar Niemeyer, with a structural project by the engineer Joaquim Cardozo. It is one of the three monumental buildings that define Praça dos Três Poderes, the others being the Planalto Palace and the Federal Supreme Court. A semi-sphere on the left (seat of the Senate), a hemisphere on the right (seat of the Chamber of Deputies) are arranged on a horizontal platform-block and, between them, two twin office towers (the so-called "Annex 1"), that rise to a height of one hundred meters. The congress also occupies other neighboring buildings, some of them interconnected by a tunnel. The building is located in continuity with the Monumental Axis, the main avenue of the Brazilian capital, as conceived by Lúcio Costa. In front of it is a large lawn, used by the population as a stage for marches, protests and other public demonstrations. At the back of the building is the Praça dos Três Poderes.