After Arabia, our heroes set course for Africa. In pursuit of Ambrosius, the climb Lalibela, in Ethiopia. There, Esteban and Tao explore a church whose walls are covered with religious murals. To their shock, one of them depicts the pyramid of Mu being carries in a procession! But the church hides something else: a strange machine from Mu. Convinced this machine will provide them with a clue leading to the next city of gold, Tao is hesitant to leave, against the advice of Esteban who suspects a trap laid by Ambrosius. Rightly so...

At Lalibela, Zia uses all her mental energy to create a force field and free Esteban and Tao from the rubble of the church. As night falls, Zia has a strange, piercing dream, plunging her into an incredible vision of an African mask leading her to a city of gold.

Arriving at the city of Kilwa, out heroes split up to find the famous Cinza. While exploring the city, they discover the sad reality of the slave markets. Moved, Zia convinces Mendoza to help them free the captives.

After having proposed to Esteban that they join forces to find the fifth city of gold, the deceitful Gomez sends his men to capture our heroes. But only Mendoza and Esteban fall into their hands. So the others are able to execute their plan to help free the captives at Kilwa threatened with being sold into slavery. Finally, Mendoza fights Gomez in a duel while Esteban steals the map leading to the city of gold. Meanwhile, Ambrosius heads for a secret base where a surprising welcoming committee awaits him...

Guided by the map stolen from Gomez, our heroes are flying over the city of Zimbabwe when, believing they have been beaten by Ambrosius, Esteban crashes. The children are taken to the palace gardens of the king Neshangwe. Seeing Zia's medallion, the king shows them "The Gate of the Ancients", a very old orichalcum arch. Thanks to their medallions, our young heroes pass through the mysterious arch which teleports them to Francis I, the king of France, in his castle at Chambord...

Teleported to Chambord thanks to the gate of the ancients, Zia and Esteban are welcomed by the king of France, meanwhile Tao makes the acquaintance of Nostradamus in the workshop of the founder of the Order of the Hourglass, the late Leonardo da Vinci. Back in Zimbabwe, the two sailors discover some hidden gold and Mendoza speaks with Laguerra, imprisoned on the ship by Ambrosius.

Thanks to the clue in the base of the pyramid of My they found in Chambord, our heroes discover the location of the fifth city of gold. But Tao, full of doubt, decides to remain in Chambord to think and find himself, rather than leaving with his friends. So, without him, the Golden Condor takes off in pursuit of Ambrosius. Once again, he has a large head-start. Unfortunately for the alchemist and his companions, the city's defences prove remarkably sturdy...

Having rid themselves of the threat of Magon the Olmec, the children are hot on the heels of Ambrosius who has opened the city of Ophir thanks to his medallion. A bitter fight for the city's treasure begins: the stone of Ophir, also known as the philosopher's stone. Meanwhile in Chambord, Nostradamus shows Tao the treasure of Chambord: a double-helix staircase designed by his master Leonardo da Vinci. But what secret does it hide?

The fifth city of gold is swallowed up as our heroes confront Ambrosius for the Stone of Ophir. A great maelstrom consumes the city and all are swept away. Carried by the flood, they are strewn here and there, all over the banks of the river. While Esteban helps the Olmec Tyrias, Zia is forced to rescue the Eternity Stone from the grip of Ambrosius. Alas, in vain...

Chasing a young boy, who has kidnapped Pichu, back to his village, Esteban and Zia find Mendoza and the sailors safe and sound. Meanwhile, Ambrosius heads for the Olmec base to repair his ship, sabotaged by Magon.

En route to Kilwa, Zia finds a stowaway in the hold of the Golden Condor: Temba, still looking for a great feat to accomplish. With his help our hero retrieves the Bako, a sacred mask stolen by Gomez. Placing it over her face, Zia has another vision in which Tao is in great danger. Despite this however, Tao is safe and sound in Chambord where he too has made some discoveries: according to the clues left behind by Leonardo da Vinci, the seventh city of gold does not exist. It is up to them to build it!

In the Lenje village, Zia, Tao and young Temba are welcomed with great fanfare. Impressed by Zia and her link to the sacred mask, the matriarch confirms that she is the one who must take the Bako back to the place where it was made, the mythical city of Orunigi.

After Ambrosius's disappearance, Laguerra and Gaspard are almost killed in the volcanic fault. They manage to escape but the heavily damaged flying ship crashes shortly thereafter. Meanwhile out heroes follow the path of the Bako to the mythical city of Orunigi where, according to the legend, the sacred mask was made.

The Leopard-men set fire to the village to create a distraction enabling them to kidnap Zia along with the sacred mask. Out heroes learn that she is being held by the powerful sorceror N'Deye, in the city of Tellem, abandoned for centuries at the foot of the Bandiagara escarpment. Jealous of the link between Zia and the Bako, the sorceror tries to force her secret from her. But, faced with his prisoner's silence, N'Deye has her taken to one of the caves in the Cliff of Spirits. While at the top of the cliff, Esteban and Tao attempt to climb down and save their friend, Zia explores the caves to try to find another exit.

Esteban and Tao find Zia in the caves of the Cliff of Spirits where the sorcerer N'Deye has imprisoned her. Together, our heroes explore the depths of the cliff and find a secret gallery where the statues grouped around Princess Rana'Ori reveal to them the location of the sixth city of gold. Meanwhile, Mendoza, Pedro and Sancho attack the sorceror and his Leopard-men to retrieve the precious Bako. Reunited once again, Esteban and his companions set out for the city of gold. But while using the sacred mask again, Zia unleashes a terrible storm...

Caught in a lightning storm, the Golden Condor crashes into the impenetrable forest of the Congo. There, our heroes are met by the guardians of this place, gorillas who escort them to the heart of their kingdom, next to a seemingly bottomless chasm. The Bako then guides Esteban, Zia and Tao to its home: Orunigi, the sixth city of gold, which to the children's great joy, opens to them. At the peak of this incredible tree-city, they find princess Rana'Ori who finally reveals to them the true goal of their mission: use the great heritage of Mu and Atlantis to prevent a great cataclysm which could destroy humanity!