Frustrated with the ongoing rebellion of the Gauls, Julius Caesar devises a new scheme to conquer them: the construction of a city of luxury apartments dubbed “The Mansions Of The Gods” in the forest near the Gauls' village as a means to absorb them into Roman civilization.

During a boar hunt, Asterix and Obelix discover the Mansions’ construction site. Project leader and architect Squaronthehypotenus and the Roman legion commanded by Centurion Somniferus order slaves to deforest the surrounding area. Asterix and Obelix attempt to counteract the Romans’ efforts using magic acorns from Getafix the druid, which instantly sprout into full trees upon planting.