Mafra stood as a monument to regal power, even though it would become only a pleasure palace and never a seat of authority. John commissioned numerous operas, comedies, and serenades to be celebrated at the palace with great pomp, and its enormous property became the favoured hunting grounds of the royal family for centuries to come. The king also began to celebrate his birthday annually at Mafra, starting in 1732. John housed one of the largest and most sumptuous libraries in Europe within the palace, with over 36,000 volumes dating from the 14th to the 18th centuries. Works at Mafra would continue until 1755, when the devastation wreaked by the Great Lisbon earthquake required as many workers as possible to rebuild the city. At about this time, also, the supply of gold and diamonds from slave labour in Brazil, used to fund John V's projects, started to dry up.