In the 16th century, Spanish Conquistadors established seven “Gold Cities” in the Audiencia de Quito in the Viceroyalty of Peru in what is now Ecuador. Records in the Archives of the Indies in Sevilla, Spain and the Apostolic Library of the Vatican indicate that these cities were extremely lucrative gold producers. However, by the beginning of the 17th century, these cities had disappeared. Five of these were rediscovered by the end of the 20th century, but two of them, Sevilla del Oro and Logroño de los Caballeros, remained lost into the 21st century. In 2016, Aurania, a Canadian mining exploration company, began its search for these lost cities. On June 6, 2022, Aurania announced that Logroño, reputed to be the richest of the seven gold cities, had been found along the Rio Santiago in Ecuador in the high likelihood area of Metron’s probability map for the location of Logroño. How did Metron develop this map? Answer: By applying Bayesian search theory methods to old Spanish records and maps and combining that information with modern geophysics and geochemistry.