The Palace has undergone many reconstructions since it was originally built by Cortes in 1523 on the ruins of Montezuma's Palace. The present structure dates from after the fire of 1692. It occupies four large blocks facing the central square in Mexico City. In July 1929, Rivera commenced work on his comprehensive history of the Mexican nation (History of Mexico) with a series of murals on the main stairway of the Palace. After several years in the United States, he returned and in 1935 he completed his murals on the stairs in the Palacio Nacional.