We think we know it when we see it. But how, pray, do we define beauty? The ancient Greeks thought they had the measure of it. In the 4^th century BC, the “chief forms of beauty,” according to Aristotle, were “order, symmetry and clear delineation.” A century earlier, during the golden age of Athens, Polykleitos, one of the ancient world’s greatest sculptors, set out the precise ratios for the ideal male form in a treatise he called The Canon.

Last year the London stage was treated to an electrifying Medea and an intelligent, refreshing Electra, at The National and the Old Vic respectively. Now it’s the turn of the Barbican to unleash the formidable force of Greek tragedy upon us, switching from Euripedes to Sophocles and a heroine who, compared to those others, is a pure-hearted innocent.

Wicked women have always sold well, but more than that, they have fired the artistic imagination in a quite exceptional way. Exploring the depiction of the witch from the 15th to the 19^th century, this exhibition is packed with images that must number amongst the most dramatic, atmospheric and gripping ever made, proof if it were needed of the energising effects of a truly inspiring subject.

A Grecian palace on a studio lot. Gods wander about among the plywood and polystyrene looking deific. As a child is raised to the heavens a voice(over) is heard to intone the following legend.

Oracle: You don’t want to believe those myths you’ve read in boys’ own books about the heroes of ancient times. That Roger Lancelyn Green is so tediously on-message. Take the dozen labours of the demi-god Hercules…

We know how the story ends, but then so did Euripides' first audience in Athens in 431 BC. Medea was already a familiar character of myth, a sorceress whose ungovernable passion for Jason led her to commit horrible murders when he abandoned her for another woman. Now, as in the Golden Age of Greek drama, the chief interest is in the way the tale is told. And the National Theatre has assembled quite a team for the purpose.

By picking his way through Homer’s Iliad and Odyssey, and Virgil’s Aeneid - written 600 years later - Simon Armitage has it all, including the horse and Helen, each of whom in their way enable the hordes to breach Troy’s gates. What with that and the mingling of mortals and gods, not to mention the 100,000 troops that Agamemnon leads across the Aegean to rescue Helen, there’s a lot to attempt to pack into this theatre’s intimate space in three hours. Rather too much as it turns out.

It’s been a bloody week on the London stage. First Titus Andronicus maims and mutilates at the Globe, and now at English National Opera Frank McGuinness and Julian Anderson bring us a distillation of Sophocles’ three Theban plays, complete with eye-gouging and assorted hangings. But while Lucy Bailey found eloquent meaning in Shakespeare’s brutality, could Anderson do the same in this, his first opera?

300: Rise of an Empire is the follow-up to perhaps the most homoerotic film of all time, 300 - a film whose obsession with the well-lubricated muscularity of the male form was matched only by its unabashed exaltation of ultra-violence (rendered endlessly and often tediously in slow-mo). It was hardly high art or sound history, but it had aesthetic bravado and a certain logic, with the strangely sexy battles effectively evoking the Spartan idea of a glorious death.

Ancient Greece has been having a bit of a run lately what with Dr Michael Scott’s recent primers on Greek culture and society and the like. There are, however, certain parts of the television audience a Hellenistic scholar cannot reach, and they are to be found on a sofa looking for something to watch between Strictly and Casualty. In the event that such viewers choose not to gorge on The X Factor, they can now opt to spend time in Atlantis. Or should that be "Atlantis"?

Having boundaries actually sets us free. So Neil Armstrong's wife argues. She is dogmatically keen to stop her husband rocketing off to the moon in the first scene of The Lightning Child – a groundbreaking show in so far as it's the first musical to premiere at Shakespeare's reconstructed wooden "O", opening last night. Armstrong (Harry Hepple in a space suit) does not agree with his spouse's imposed limits, however. A lunar voyage is, he says, his chance to become sublime.