Founded in 1533, Cartagena gained fame after the mid-16th century when great fleets stopped annually to take on gold and other products to convoy to Spain. In 1811, Columbia declared its independence from Spain. In the early national period, Cartagena was handicapped by inadequate connections with the interior, and by the 1840s it had declined in population and commerce. In the 20th century Cartagena experienced renewed growth due to the oil fields in the Magdalena Valley and is now Columbia's fifth largest city, with 850,000 inhabitants with a bustling maritime and industrial center. Yet visitors find themselves transported back in time as they wander the twisting streets of the old city, and climb the massive walls off the fortress of Castillo de Felipe de Barajas, rising 135 feet above sea level.