Sophia Loren as the emperor's daughter Lucilla - framed by Mann in lots of fascinating shots swathed in furs and against imposing backgrounds. Stephen Boyd fills out the hero role (it wouldn't have been quite right for Heston) and Christopher Plummer makes for a devious rather insane imposter to the throne, as it turns out he is not the son of Aurelius at all! Mel Ferrer, John Ireland, Omar Sharif and Anthony Quayle fill out the other leading roles as the empire is lost as Rome is conquered from within.
It is interestingly done and is probably the last of the big epics of the early '60s, following SPARTACUS and CLEOPATRA. Anthony Mann also directed EL CID and this is more of the same, also from producer Samuel Bronston. Further "epics" like 55 DAYS AT PEKING or the rather tatty GENGHIS KHAN were just not in the same league.
So, the last of the big ones then - and the starting point for the later GLADIATOR, though CGI spectacles are just not the same (see TROY for instance!). It must have been an important movie for Loren - she had started off 14 years earlier as an extra in QUO VADIS in 1950, and now here she was headlining her own roadshow epic! Alec Guinness is very interesting in his autobiography on taking Loren out to dinner during the shoot - 20 years earlier she may well have been one of the hungry children in Naples whom he was giving food to when in the English army during WWII!