Royal Palace · Madrid de los Austrias
The largest royal palace in Europe exists because the old one burned down on Christmas Eve
The Royal Alcázar, a fortress first built by the Emir of Córdoba in the 9th century, burned down on Christmas Eve 1734. Spain's new Bourbon kings replaced it with a palace of 3,418 rooms, built almost entirely of stone between 1738 and 1755. Charles III was the first king to live in it.