The sun burns in the Andes highlands, while our friends cross an arid desert. They head for the mountain supposed to house the City of Gold, indicated by Karuga, the chief of the Urubu tribe. Sheltered in the shade of a rock, the group pauses to rest and drink. Suddenly, Kokapetl alerts them. A huge hand, then a giant figure appears: Esteban then recognizes Karuga.
Exhausted and certainly hurt, the giant asks to drink. Despite the reluctance of Sancho and Pedro, Esteban and Zia sacrifice their water rations for his benefit. Karuga claims that his tribe banished him after the failed attack on the village of Tetola. In order to thank him for his generosity, Karuga warns Esteban that the Urubus are planning an ambush to capture Zia and offer it as a sacrifice to their goddess, Pachamama. Karuga adds that there is a way to avoid them: the Valley of the Dead, feared by the Uruu tribe.
When Esteban asks Karuga what he plans to do, he says he has to go far, probably to another country. And despite the boy's worries about him, the fallen giant walks away under the burning rays of the Andean sun. Mendoza reminds Tao that he hasn't drunk his water ration. As a sign of friendship, the three children decide to share it, then walk again.
Karuga was right: the giants follow our friends very closely. Two heavy bronze arrows suddenly land in a rock. All are aware of the threat and flee towards the valley indicated by Karuga. They realize that this valley is filled with sulfur vapors. Luckily, gas fumes are projected towards the giants, which allows our friends to escape. Finally this is thee end of the valley and all are safe.
The day comes to an end and Zia notices that the sun will end its race between two rocky peaks in the distance. The wonderment of the children is redoubled when a powerful ray of light is projected in the direction of the mountain they want to reach. Esteban remarks that a scintillating point appears on this mountain. Zia compares it very aptly to "a star shining in the mountain". Esteban then thinks at the Koyolite star he heard about at High Peak. All climb towards this "star" and come face to face with a stone statue of the goddess Pachamama, adorned with a sapphire on the forehead. Esteban remembers that to allow the doors of the Cities of Gold to open, it is necessary that the two medallions are placed on the chest of the goddess of Earth.
Mendoza understands and actually notices two locations on the goddess' chest. The children place their pendants and the mechanism is triggered: the earth begins to tremble, the wall of the mountain opens in two parts and all then see a splendid city bathed in the setting sun. They have just discovered the city of Tseila! Fooled by the sunset, they deduce that it is a City of Gold, but the nightfall makes them understand that it is only an abandoned stone city. In the central temple, all discover a huge empty room. Tao notices the emblem of the sun engraved on a wall with a gold part. Esteban notes that this is a medal that stands out exactly like his pendant. The boy takes the gold part and a new mechanism is triggered: the whole room is suddently flooded with an extremely dazzling light. When they open their eyes, everyone can contemplate a gigantic bird entirely out of gold, enthroned in the center of the room, appeared as if by magic.
Mendoza dares to believe his eyes until he has touched it. How not to believe in the Cities of Gold in the face of such a marvel?