Like another reviewer stated, this is a respectable but highly flawed film adaptation of the play "The Tragedy of Julius Caesar". The performances are respectable enough, depending on the actor one references. Charlton Heston does a great job, but Robards performance as Brutus doesn't weigh in until about half way through the drama, and seems to be a little undirected for the first half of the play. It seems like a lot of the money that went into this project went into paying the actors' salaries, for the art direction gets the period wrong in several places, and puts Marc Antony's famous speech on an indoor set instead of an outdoor plaza as was meant.
The most jarring for the military afficionados is the inappropriate armor and armament for the soldiers. The generals wear naval hats, and the armor is some kind of mish mash from other periods in history. I can only guess that this was done because the director liked the style (which was common for this period in film making for Hollywood to take such atrocious liberties with history).
It's worth it for seeing Chuck Heston's Marc Antony, but the version with Marlon Brando some yhears earlier (shot in black and white) is the one to see.
For all it's flaws, and there are many, this 1970 version staring Heston is worth a look. Heston plays Marc Antony as a passionate loyalist who seethes with the angst of betrayal, and does an ecellent job of it. Gielgud's Julius Caesar is solid, but I think the audience deserved someone with more gravitas and "a martial countenance", to borrow from the language of the time.
See it once.