Proposals for a canal across the Isthmus of Panama date back to 1529, soon after the Spanish conquest. Álvaro de Saavedra Cerón, a lieutenant of conquistador Vasco Núñez de Balboa, suggested four possible routes, one of which closely tracks the present-day canal. Saavedra believed that such a canal would make it easier for European vessels to reach Asia. Although King Charles I was enthusiastic and ordered preliminary works started, his officials in Panama soon realized that such an undertaking was beyond the capabilities of 16th-century technology. One official wrote to Charles, "I pledge to Your Majesty that there is not a prince in the world with the power to accomplish this". The Spanish instead built a road across the isthmus. The road came to be crucial to Spain's economy, as treasure obtained along the Pacific coast of South America was offloaded at Panama City and hauled through the jungle to the Atlantic port of Nombre de Dios, close to present day Colón. Although additional canal building proposals were made throughout the 16th and 17th centuries, they came to naught.