A major part of Bucharest's architecture is made up of buildings constructed during the Communist era replacing the historical architecture with high-density apartment blocks – significant portions of the historic centre of Bucharest were demolished to construct one of the largest buildings in the world, the Palace of the Parliament (then officially called the House of the Republic). In Nicolae Ceaușescu's project of systematization, new buildings were built in previously historical areas, which were razed and then built upon.