In the exploration of the Peruvian territory during the conquest, the rivers Amazonas, Ucayali and Madre de Dios were discovered by the Spaniards.

Discovery of the Rio Grande de las Amazonas

In search of the Country of the Cinnamon, Gonzalo Pizarro left with 180 Spaniards and 3 thousand Andeans from Cuzco. At the end of 1580 he arrived in the city of Quito and appointed as deputy Francisco de Orellana, founder of Santiago de Guayaquil. In the Coca River, which he called Santa, Pizarro ordered the construction of the brig San Pedro, which Orellana would lead, while he would march along the shore. When it was doubted that the mythical country was close and food was becoming scarce, Orellana offered to look for them. Gonzalo Pizarro accepted with the condition that he return in 12 days. At the command of 57 men, Pizarro's lieutenant departed on December 26, 1541, eastward along the Napo River. After passing the confluence of Curacay, they came to a river called Rio Grande, later Río Grande del Amazonas. They stayed in the town they named Aparia, where they built another brig that they named Victoria.

At the mouth of the Madeira River, on June 10, 1542, they captured a man who said he was a vassal of warrior women who in the European imaginary were identified as the Amazons of ancient Greek tales. The confrontations with the natives were intense, until finally on August 26, 1542, Orellana and his crew arrived in the Atlantic Ocean. They went to Hispaniola in Santo Domingo, then arrived in May 1543 in Valladolid.
Before the Council of the Indies and Prince Felipe, Orellana requested authorization to carry out the conquest of the Amazon as an advance. On the way to his next project, Francisco de Orellana died in November 1546, of a strange disease in Nueva Andalucia (Venezuela).

Discovery of the Ucayali River

Juan de Salinas Loyola was a seasoned Spanish captain, born in Valladolid, who participated in various expeditions and conquests, including Chachapoyas. On July 8, 1557, after obtaining the respective permit from the Spanish Crown and commanding 250 men willing to do everything, he left Loja (now Ecuador) and went into the Peruvian jungle in search of gold. It crossed the today called mountain range of the Condor, raffled the pongo of Manseriche, navigating the Marañón river, and after another year of crossing, on September 29, 1558 it reached the Ucallale river (* confluence * in pano language). Salinas and his people baptized this huge river with the name of San Miguel. With several losses among his hosts, a rather thin booty and a deplorable state of health, Salinas returned without greater reward than an audience in the Crown, which granted him the governorship of the lands discovered.

Discovery of the Madre de Dios or Amarumayo River

The river of the serpents (amaru, snake, mayu, river), today known as the Madre de Dios river, was discovered by the Spanish captain Álvarez de Maldonado in 1566, who agreed to it in search of the legendary Paititi, a sort of El Dorado of the south Amazon. Years before, the captain of Greek origin Pedro de Candia, commanding an army of three hundred well-armed men, and Pedro Anzures de Campo Redondo, with an impressive trousseau of travel and cavalry, had two failures in their attempt to cross the dense jungle and get to this river. At that time it was said that the lands around the Mother of God kept huge treasures.

Álvarez de Maldonado, who bequeathed his surname to the future capital of Madre de Dios, confronted a certain Gómez de Tordoya in the middle of the Amarumayo jungle. Few could survive, among them Álvarez Maldonado, who was lucky to be guided by the Indians to leave the area by Carabaya, heading to Cuzco.