The commercial prosperity of Majorca, derived from the enterprise of her sailors, led to the building of the _Lonja_, or Exchange, which is still one of the chief architectural ornaments of Palma. The architect was Guillem Sagrera, who also built the Castel Nuovo at Naples for Alfonso V.; and the work was undertaken by the principal merchants of Palma. Finished in 1450, it consists of a lofty hall with a groined roof supported by six tall slender pillars. The doorway is very richly carved in the style of the north door of the cathedral, and at each angle of the edifice there is a statue of a saint under a stone canopy: San Nicolas in the angle facing Porto Pi, in the opposite niche San Juan Bautista, in the angle looking towards the Ataranza (arsenal) Santa Catalina, and Santa Clara looking towards the Almudaina.[21] Here was the centre of commercial transactions during the Middle Ages, while the wharves outside formed an active and busy scene, the ceaseless ebb and flow of Mediterranean trade. The commercial ventures were not without danger, the piratical States of Barbary continuing their raids and depredations quite into modern times. Barbarossa infested the seas and caused such havoc that the Emperor Charles V. undertook punitive expeditions to Tunis in 1535 and to Algiers in 1541. On the latter occasion he landed at Alcudia, and proceeded thence to Palma on October 13. He was received with great demonstrations of joy by all the chief people of the island, Nicolas Cotoner and Pedro Juan de Santa Cilia, bearers of most ancient names, walking by his horse to the cathedral, where Mass was said. The Emperor was received in the Almudaina, and Leonardo Zaforteza superintended the arrangements for lodging the other guests. Charles departed on the 18th, taking with him a hundred Majorcan knights who joined his expedition. But the elements were against them, and the invasion of Algiers ended in failure.