The particular, moribund atmosphere of Sunday in Belfast endures tenaciously, in spite of all talk of renewal and reinvigoration. Even on the opening weekend of the 35th Belfast Festival at Queen's, the art galleries were closed on Sunday, the Fringe had developed a bald patch - and it was impossible to find a decent espresso . . . Walking through the deserted streets on the way to The Waterfront Hall, there was a sense of unreality, as if the Romanian production of Aeschylus's Oresteia that was about to begin there belonged to an entirely different world. The impact on any city of a broadly based, three-week, multi-arts festival is bound to be nebulous and difficult to assess, with parallel strands - dance and jazz, at the opening weekend - taking place without audiences intersecting, but in Belfast the question: "where is the festival?" seems particularly pertinent. Building and nurturing a local audience for the festival's undeniable riches remains a challenge, which this year has been partially addressed by the inauguration of a Fringe festival in parts of the city usually untouched by the arts, and by the introduction of a series of workshops given by visiting international companies - The Wooster Group, Philip Glass and Trisha Brown - to local artists.

Following last year's massive expansion of the festival, under the directorship of Sean Doran, some of the most prestigious companies from the international arts festival circuit are again landing in Belfast over the next three weeks, and of these, Silviu Purcarete's National Theatre Of Craiova is a star attraction. Following his adaptations of Les Danaides and Phaedra, Purcarete has turned his attention to Aeschylus's influential trilogy of revenge, retribution and reconciliation, (Agamemnon, Choephoroi and Eumenides) based on the Homeric epics and first staged in 5th century Athens.

Rarely performed in this part of the world (the last time was the National Theatre's production directed by Peter Hall in 1981) the trilogy poses enormous challenges for audiences, performers and directors. Purcarete has weighed in fearlessly and irreverently, slashing each play, especially the second, and reducing the whole to 160 minutes, creating his own version of the trilogy, rather than an adaptation. The stage imagery he has created is startlingly arresting - clear, simple and effective. At other times the crudeness of his direction and dramatisation jars. Orchestral music is used bombastically and melodrama and pantomime threaten to erupt at moments, such as when the blood-spattered Clytemnestra is moaning triumphantly over the corpse of Agamemnon, and when her lover Aegisthus hacks off some of Agamemnon's flesh and eats it. As in his other productions, Purcarete has paid particular attention to the beautifully choreographed movement and humane responses of the chorus. In the opening play (Agamemnon) the chorus is a group of grey-suited old men with briefcases, shuffling, whispering and snickering, thrilled and appalled at the bloodshed around them; later the ancient deities, the Furies (in Eumenides) are portrayed as heavily pregnant women, clad in white body stockings. There's a surprising amount of humour too, rooted in the chorus's gestures and body language.

The essential plot remains intact: the return of the Greek leader, Agamemnon, from the Trojan War, his murder by his wife Clytemnestra, the murder of her, in turn, by their son Orestes, and the judgement and acquittal of Orestes by the Athenian jurors, presided over by the city's patron goddess, Athena. But most of the cultural and religious contexts have been excised: the lengthy, dense, allusive speeches of the chorus have been heavily cut, and the language, translated from Ancient Greek to Romanian and then into English for the surtitles, has a prosaic bluntness that will make purists wince. Does this matter? Obviously Purcarete is aiming to simplify, and to communicate the central themes of these plays to the widest possible audience, breathing life into ancient texts and treating them as if they were written yesterday. Yet, so much has been lost, so much dignity, ritual, formal symmetry, mystery, poetry - so much that is particular to Greek tragedy, yet still has extraordinary resonance - that it's hard not to think that the audience is being presented with a spectacle shorn of its significance, and that this seminal and enduring work has not been sufficiently well served. If the Oresteia were staged more frequently, this problem would disappear: we could have multiple approaches, interpretations and adaptations. And of course, it might be possible to find a middle way (in the best Greek spirit) between Peter Hall's painstakingly accurate historical recreation of the world of Greek theatre, complete with male actors and masks, and this radical, visually potent, re-invention.

Much has been made of the parallels between the (ambiguous) endorsement of democracy, justice and peace at the end of Aeschylus's trilogy and the inauguration of a new political phase in Northern Ireland. The Oresteia, however, is bigger than any single historical context, even that in which it is rooted. The play at this year's festival which does have enormous topicality and resonance for Belfast, however, is the new production of Stewart Parker's 1798 play, Northern Star, staged in the First Presbyterian Church in Rosemary St, where leaders of the United Irishmen met in secret 200 years ago. A co-production between Tinderbox and Field Day companies and the festival, it is directed with clarity and conviction by Stephen Rea, with the setting adding to the moving sense of occasion and anticipation on the opening night. In many ways, this is a difficult play, structured as a series of flashbacks, with abrupt temporal as well as stylistic shifts. As the United Irishmen's leader in Antrim, Henry Joy McCracken (memorably played by Conleth Hill) relives the events of the preceding decade, key scenes from the progress of the revolutionary movement are re-enacted. These are written in the dramatic styles of Farquhar, Boucicault, Wilde, Shaw, Synge, Behan and Beckett, in a dazzling display of theatrical ventriloquism. The performances have energy and wit which infuse these scenes with life, and the entire production has a celebratory tone, suggesting an act of reclamation and restoration: reclamation of memory from sectarianism's selective amnesia, and restoration of the place of Ulster Presbyterianism in the history of the United Irishmen's egalitarian ideals.

This riveting production alone, with its inspired choice of setting, made a visit to the festival worthwhile. Other notable events were a Saturday morning recital by the Swedish mezzo, Katarina Karneus, singing lieder by Mahler and Schumann, and beaming delightedly as if astonished by the glorious sounds emitting from her own throat; the Ulster Theatre Company's atmospheric but uneven staging of T.S. Eliot's Murder In the Cathedral in the icy vaults of St Anne's Cathedral; on the Fringe, Darragh Carvill's Language Roulette, a droll recreation of a typical night out in the pub, with secrets being blurted and friendships destroyed; Yoko Ono's perspex maze, Amaze, at the Ormeau Baths Gallery, and above all, Bill Viola's video installation, Nantes Triptych, at Portview Trade Centre, evoking, through three moving images, the entire cycle of life and death. This characteristically meditative and mysterious work embodies what the novelist and filmmaker, Clive Barker, said to the packed audience at his public interview on Friday night: the point of making art is "to allow people to feel the `otherness' we feel as children, so that we're alive to nuances in the world that make us strange to ourselves." Two and a half more weeks of estrangement follow . . .

The Belfast Festival at Queen's runs until November 1st. To book phone Belfast 665577