La nave volante

The Atlantean city of Ol Undas, which remained hidden for millennia on the top of a very high cliff, was destroyed (and all its inhabitants killed) by monsters artificially created by Saltur, a scientist intent on making it his personal army to seize power and set off to conquer the world. To defeat the threat of the monsters remaining on the stone tower, led by a primate leader called Serkis who seems to have superior intelligence, Zagor and Scarlet (the adopted daughter of the flight pioneer Icarus La Plume) drive a flying machine designed by the Baron to Ol Undas, escorted by a team of soldiers.