Louvre, (properly, Musée du Louvre), national art museum of France and the palace in which it is housed, located in Paris, on the right bank of the Seine River. The structure, until 1682 a residence of the kings of France, is one of the largest palaces in the world. It occupies the site of a 13th-century fortress. The building of the Louvre was begun in 1546 in the reign of Francis I, according to the plans of the French architect Pierre Lescot. Additions were made to the structure during the reigns of almost every subsequent French monarch. Under Henry IV, in the early 17th century, the Grande Galerie, now the main picture gallery, which borders the Seine, was completed. Under Napoleon III a wing on the north side (along the rue de Rivoli) was finished. By the mid-19th century the vast complex was completed; covering more than 19 hectares (48 acres), it is a masterpiece of architectural design and sculptural adornment.