In 1513, about 40 miles south of Acandí, in present day Colombia, Spanish Vasco Núñez de Balboa heard unexpected news of an "other sea" rich in gold, which he received with great interest. With few resources and using information given by caciques, he journeyed across the Isthmus of Panama with 190 Spaniards, a few native guides, and a pack of dogs. Using a small brigantine and ten native canoes, they sailed along the coast and made landfall. On September 6, the expedition was reinforced with 1,000 men, fought several battles, entered a dense jungle and climbed the mountain range along the Chucunaque River from were this "other sea" could be seen. Balboa went ahead and, before noon September 25, he saw in the horizon an undiscovered sea, becoming the first European to have seen or reached the Pacific from the New World. The expedition descended towards the shore for a short reconnaissance trip, thus becoming the first Europeans to navigate the Pacific Ocean. After traveling more than 110 km (68 mi), Balboa named the bay where they ended up San Miguel. He named the new sea Mar del Sur (South Sea), since they had traveled south to reach it. Balboa's main purpose in the expedition was the search for gold-rich kingdoms. To this end, he crossed through the lands of caciques to the islands, naming the largest one Isla Rica (Rich Island, today known as Isla del Rey). He named the entire group Archipiélago de las Perlas, which they still keep today. In 1515–1516 Juan Díaz de Solís sailed as far as Río de la Plata, which he named, having died trying to find a passage to the "South Sea" in South America at the service of Spain.
Since 1516, several Portuguese conflicting with king Manuel I of Portugal gathered in Seville, at the service of the newly crowned Charles I of Spain. Among them were explorers Diogo and Duarte Barbosa, Estevão Gomes, João Serrão and Ferdinand Magellan, the cartographers Jorge Reinel and Diogo Ribeiro, the cosmographers Francisco and Ruy Faleiro and the Flemish merchant Christopher de Haro. Ferdinand Magellan—who had sailed in India for Portugal until 1513, when Maluku Islands were reached, and kept contact with Francisco Serrão living there—developed the theory that the islands were in the Tordesillas Spanish area, supported on studies by Faleiro brothers. Aware of the efforts of the Spanish to find a route to India by sailing west, Magellan presented them a plan to get there.
The Spanish king and Christopher de Haro financed Magellan's expedition. On August 10, 1519, departed from Seville a fleet of five ships—flagship Trinidad under Magellan's command, San Antonio, Concepcion, Santiago and Victoria, the first being a caravel, and all others rated as carracks or "naus"—with a crew of about 237 men from several nations, with the goal of reaching the Maluku Islands by traveling west, trying to reclaim it under Spain's economic and political sphere.
Victoria, the single ship to have completed the first world circumnavigation.
The fleet sailed further and further south, avoiding the Portuguese territories in Brazil, and become the first to reach Tierra del Fuego at the tip of the Americas. On October 21, starting in Cape Virgenes, began an arduous trip through a 373-mile (600 km) long strait that Magellan named Estrecho de Todos los Santos, modern Strait of Magellan. On November 28, three ships entered the Pacific Ocean—then named Mar Pacífico because of its apparent stillness. The expedition managed to cross the Pacific. Magellan died in the battle of Mactan in the Philippines, leaving the Spaniard Juan Sebastián Elcano the task of completing the voyage, reaching the Spice Islands in 1521. On September 6, 1522 Victoria returned to Spain, thus completing the first circumnavigation of the globe. Of the men who set out on five ships, only 18 completed the circumnavigation and managed to return to Spain in this single vessel led by Elcano. Seventeen other arrived later in Spain: twelve captured by the Portuguese in Cape Verde some weeks earlier and between 1525–1527, and five survivors of the Trinidad. Antonio Pigafetta, a Venetian scholar and traveler who had asked to be on board and become a strict assistant of Magellan, kept an accurate journal that become the main source for much of what we know about this voyage.
This round-the-world voyage gave Spain valuable knowledge of the world and its oceans which later helped in the exploration and settlement of the Philippines. Although this was not a realistic alternative to the Portuguese route around Africa (the Strait of Magellan was too far south, and the Pacific Ocean too vast to cover in a single trip from Spain) successive Spanish expeditions used this information to travel from the Mexican coast via Guam to Manila.