And so began one of the greatest cartoons of all time. Here is the basic info on the show:
The Mysterious Cities of Gold (太陽の子エステバン ,Taiyō no Ko Esuteban?, lit. Esteban, a Boy from the Sun), abbreviated MCoG, is an anime series co-produced by DiC Entertainment and Studio Pierrot. The series premiered in Japan on NHK on May 1, 1982 and ran for 39 episodes until its conclusion on September 5, 1983. It was licensed for release in France by AK Video, which aired the series under the title Mystérieuses Cités d'Or in 1983. The French version, edited to have different characterization and music, was subsequently redubbed and distributed to many different countries throughout the world. In the United States, it aired under its English title of The Mysterious Cities of Gold. It is licensed for English language home video release in the United Kingdom, North America, and Australia by Fabulous Films. Set in 1532, the series follows the adventures of a young Spanish boy named Esteban who joins a voyage to the New World in search of the lost Cities of Gold and his father.The show is based in part on actual history and loosely based on Scott O'Dell's book The King's Fifth albeit with a Sci-Fi twist. Here is the basic info on the book:
In 1532 a Spanish orphan named Esteban joins Mendoza, a navigator, and his associates Sancho and Pedro, in their search for one of The Seven Cities of Gold in the New World, hoping to find his father. They are joined on their quest by Zia, an Incan girl, and Tao, the last descendant of the sunken empire of Mu (Hiva in the English dub).
The series is a mix of ancient South American history, archaeology, and science fiction. The travellers encounter the Maya, Inca, and Olmecs during their journey. They discover many lost technological wonders of the Mu Empire, including a solar powered ship (the Solaris) and The Golden Condor, a huge solar-powered would-be ornithopter (mechanical bird), capable of traveling considerable distances under the sun's power alone. They are constantly pursued by antagonists Gomez and Gaspard, who are also in search of the Cities of Gold.
The King's Fifth is a children's historical novel by Scott O'Dell that was the inspiration for the cartoon TV series The Mysterious Cities of Gold. It describes from the point of view of a teenage Spanish Conquistador how the European search for gold in the New World of the Americas affected people's lives and minds.The King's Fifth is a good case study on the sin of greed and it's affect and effects on different people. Anyways, The Mysterious Cities of Gold use to haunt my dreams for years as I vaguely remember seeing it on Nickelodeon in the 80's at the 5/6 am Eastern Time time-slot. It haunted me that is until I obtained a fan-made bootleg copy a few years ago from Tim Skutt who made it and coincidentally was interviewed as an extra feature on the new official DVD. The official DVD also features all the historical documentaries that were cut from the US broadcast on Nickelodeon. Grab a copy if you can, it's good for all ages especially History buffs and Sci-Fi/Fantasy fans.
 Plot summary
The story takes place in a time when the Spanish adventurers known as Conquistadors roamed the New World of the Americas in search of the mythical gold treasures of the dethroned Native Americans.
Estéban is a teenage cartographer of the Spanish Conquistador Army. The story starts in his jail cell, where he is awaiting trial for tax evasion. More specifically, he is suspected of finding a treasure without submitting the Quinto Real, also known as the "King's Fifth", a tax levied by the King of Spain on precious metals.
Here is part of episode 1:
Here is the ending theme:
And here is an example of the very early 1980-ish documentaries that immediately followed the end of European broadcasts:
Also check out Tim Skutt's Youtube channel: skuttduck's Channel.