Caligula's Hot Nights (1977)

In Augusta the emperor Caligula has a serious problem: he must demonstrate his manliness "coram populo" on the occasion of the feast of Priapus. But the Imperial young man is powerless and threatens a fool in front of the people who arrive in droves to watch the battle. To avoid this conflict, he goes to the professor Barnardus and attempts to hide out in his clinic.