The Mysterious Cities of Gold (1982) : 4x7

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...