The Subterranean Secret Taiyô no ko Esuteban : Season 1 Episode 15

Gomez and his soldiers attack the Fort of the Black Eagle to try to recapture the cannon Mendoza had stolen. Mendoza uses the cannon to fight back, but cannot stop the Spanish army who storm the fort and drive the Incas out. Esteban, Tao and Zia run away towards the High Peak, following secret underground passages constructed by the Incas.