[1][2] He is best known for his final trip with Lope de Aguirre in search for El Dorado, where he was assassinated in a plot by a fellow officer.

He was born in Arizkun, Baztan, to a Beaumont family who supported the Spanish occupation of Navarre, benefiting directly from the Navarrese loyalist defeat at Amaiur in July 1522.

[3] Ursúa later searched the Amazon region for El Dorado with Lope de Aguirre.

[4] A fictional version of Ursúa and Aguirre's story is depicted in the Werner Herzog film, Aguirre, der Zorn Gottes and in the Carlos Saura film El Dorado.

The book provides details about the life of Ursúa and makes a general account of the events happening in the New World during the mid 16th century.