Alejandro Amenabar’s “Agora” is in some ways a throwback to the Greco-Roman epics of the fifties and sixties. But there’s a major difference. In the old Hollywood films, the Christians were the persecuted victims. In this picture they’re the intolerant persecutors. Of course, Amenabar isn’t presenting a simple anti-Christian polemic (though the extent of anger with the Catholic Church in Spain in the post-Franco era would make that understandable as well as possible). Rather he’s using the blind dogmatism of the early Christians to attack modern religious intolerance, which usually comes nowadays from a different quarter. And the point is made even clearer by the addition of an affiliated message about the oppression of women, particularly in terms of the intellectual life. Of course, this being a movie, the script adds romantic subplots and plenty of violence, though overall the piece remains oddly stolid and talky throughout.

The story is set in early fifth-century Alexandria, about a hundred years after Constantine had converted and ended the persecutions. Over the intervening century Christians had become an important, even dominant group. (By the close of the fourth century, the emperors had made Christianity the state religion of Rome and outlawed official support of the old cult.) The bishop of the Alexandrian community was Cyril, an active and energetic proselytizer and writer—portrayed here by Sami Samir as a virtual cult leader with clear political motives, a characterization that’s not all that wide of the mark. His followers, according to the screenplay, were constantly doing battle with the city’s remaining pagans (and its Jewish contingent) in the forum that gives the film its title, with the bishop’s final goal being the forced baptism of them all. To that end he and street rabble-rouser Ammonius (Ashraf Barhom) employ a bunch of fanatics, the parabolani, as hard-fisted enforcers.

Cyril’s political target is the Roman prefect Orestes (Oscar Isaac), a prudential sort of fellow who pays lip service to Christianity while actually maintaining the rationalistic attitudes he learned as a student of Theon (Michael Lonsdale) at the Great Library, where he studied alongside Theon’s brilliant daughter Hypatia (Rachel Weisz), in whom he also took a personal interest, and whom he now continues to protect in her efforts to understand scientifically the workings of the solar system. Hypatia will become the focus of Cyril’s drive for dogmatic uniformity in the city, and Orestes will find himself pressured to choose his faith over her. A counterpoint of sorts to this thread is provided by another involving Davus (Max Minghella), Hypatia’s erstwhile slave, whose advances she rejects, pushing him into the ranks of the Christian fanatics himself.

There’s a certain intrinsic interest in such an unusual tale, and it does have a historical foundation. (Hypatia was a noted Neoplatonic philosopher at Alexandria who was in fact killed by a Christian mob in 415, very likely with Cyril’s connivance.) But because of Amenabar’s pedantic, over-serious approach and his heavy-handed point-making, it’s a chore to sit through. And while Weisz shows some vitality as Hypatia, Isaac is stiffly uninteresting and Minghella, in a poorly-written part, even worse. Barhom and Samir make a stronger impression as the dictatorial true believers, and Rupert Evans is an intriguing, if opaque, presence as Synesius, the bishop of Cyrene who acts as go-between for Orestes with Cyril.

The physical production of “Agora” is impressive, with antique Alexandria recreated through a mixture of location shooting and CGI, and Xavi Gimenez’s wide-screen cinematography uses it well. But the style gets awfully arty at points—as in the sequence recounting the Christian vandalism of the Library, which ends in swirl of papyrus rolls tossed into the air—and the periodic employment of aerial shots, sometimes satellite-like views and sometimes closer-in images of the urban area, increases the detached feeling of the whole, taking as it were a God’s-eye perspective of the entire business.

Despite the open-air connotation of the title, there’s a curiously constructed, even suffocating quality to “Agora” that leaves it an interesting failure.