Disused sheds in County Wexford might seem unlikely sources of poetry, but Derek Mahon created one of his best-known poems from one, where mushrooms press towards the light of history. And from a disused coal-shed on Wexford's quays, Bui Bolg, the town's resident street theatre company, is currently pressing towards the deadline of the Opera Festival's opening night.

Precious extra funding from the Millennium Festival Committee has meant that this year, Wexford folk have the unprecedented - and one-off - pleasure of seeing major street theatre in their town for both the opening and closing nights of the festival.

It's one of the last Saturday afternoons before opening night, when the narrow Wexford streets will be filled with the sounds of arias, rustling first-night frocks, and the scampering feet of small children as they try to find the best place to watch the pre-opera outdoor entertainment. Although the coal shed is disused in the sense that it no longer hosts lumps of coal, it is most certainly being used by the 14-strong company Bui Bolg (and its shifting volunteer cast of scores) as their workshop.

Colm Lowney, Bui Bolg's manager, and Stephanie Hayes, its co-ordinator, are sitting in the tiny screened-off office. Sketches and drawings for their opening-night performance, The Ice Queen, are scattered all over the floor: Cossacks, giant icicles, swans, snowflakes, and onion-domed palaces. They have been given permission to set up their show on the section of railway track that runs between the two points of the arc at the Crescent Quay, where the statue of Commandant John Barry looks out across the water. The Crescent provides a natural viewing area.

"We'll be setting up a stage on the track," Lowney explains, "and also using the stretch of water between the track and the quayside." He adds anxiously that Iarnrod Eireann know all about this, and have made alternative arrangements for rail passengers for that night. The gauzy palace backdrop, which is currently hoisted like a sail in the workshop, will turn the railway track section regal for the night. Huge swans will float on the water. The show will start with jesters tumbling and juggling on the royal stage, watched by the King and Queen, the picture of a happy court, until - aha! Enter the villain and the time-honoured difficulties a villain does provide!

"He's this Rasputin bad magician type character that gets thrown out of the palace," Lowney says. "He takes revenge by turning everything into ice, including the princess." Most of the characters are large puppets, manoeuvred by people behind them, but the ice princess is "my sister Jenny, wearing a nightdress," reports Lowney. After the freezing of the palace and the princess, the trusty Cossacks get on the case to try to break the spell. What happens next? You'll have to be at the Crescent Quayside at about 7 p.m. in Wexford on October 14th to find out.

All this time, people are gathering in the main area of the workshop outside, waiting for their samba-drumming lesson from Fiona Glavin, of Dublin's Happy City Sambo School. They'll be the folk who'll be helping entertain the crowd before The Ice Queen starts. There are also some jesters, practising their juggling skills, and various circus tricks, including walking on a rope tied between what looks the giant axle of some truck. They shimmy across the rope with enviable ease.

"No, it isn't a tightrope," explains Seamus Kenny patiently to this reporter. "It's a slack rope. Much easier to start on. Tightropes aren't ropes at all, they're taut wires." He grins. "Would you like to try it?"

So here goes. Off with the shoes and gingerly up onto the rope. It may be called a slack rope, but it's certainly no slacker at the moment, the way it's busily quivering beneath my confused feet. Seamus is gallantly holding onto my hand to help me balance, otherwise I'd have plummeted from my perch like a shot duck.

"Keep your feet straight in front of each other," he advises. I shuffle forward. Possible future career as film-star cat-burglar, who nips across rooftops via rope tied between chimney pots seems sadly unlikely. Shuffle, swing, wobble, shuffle, swing, wobble wobble wobble. "Oh, very good," coo some onlookers, as I manage to make one or two unsteady steps. The scenario reminds me of something: my sister, praising her small son's recent first steps . . .

Back on with the shoes again, and Seamus appears with juggling balls. He hands me three and then juggles three himself. With complete confidence. "How long," I ask, "did it take you to learn that?" "Oh, about an hour," says Seamus, with happy insouciance.

I try with one first, tossing it high, and catching low. Then a second. Co-ordination is all. Throw. Wait. Throw the second as the first is coming down. Catch the second. Having already thrown the first again... I'm concentrating harder than I've done since puzzling over calculus at school. And the juggling balls are still falling. Try Again. Fail Again. Fail Again. Fail Better. Well, good thing we weren't juggling pieces of ancient Ming china.

So what are Bui Bolg's own memories of growing up with the Opera Festival? "I saw my first fireworks on the opening night of the Wexford Festival. I couldn't work out where they were going to land. We used to stand on the bridge and watch them. And then after the fireworks, we'd go and look at all the shop windows," remembers Colm Lowney. "When you're from Wexford, you get to go to the previews and dress rehearsals for a special price, so people always go to those."

"I've only ever been to one opera in my life," confesses Seamus Kenny. "And that was some Wagner in Vienna that I paid a pound to get in the back-packers's entrance to." For the first time ever this year, due to the extra funding, there will also be an open-air performance for the closing night of the festival, which will include the by-now well-beaten Millennium Drum. The closing night opera will start at the unusually early time of 5 p.m., so the opera-goers can come to the quays after to join the street party.

Wonderfully, the last night of the festival also coincides with Hallowe'en. The magical-sounding Ghost Train is a co-operative production between Bui Bolg, Macnas, and Spraoi. The idea was dreamed up by the big man with big ideas, Paraic Breathnach, and is being co-ordinated by Rupert Murray.

"We have the loan of a steam train from the Irish Railway Preservation Society," says Lowney. "Each of us is taking one carriage - they'll be freight carriages for the night, with false walls we've built ourselves. The train will start at the station, and run the half-mile through the town to Crescent Quay. It'll stop at intervals along the way, and we'll do our stuff, so the people in the crowd should be able to see everything."

Bui Bolg's carriage has a Voodoo theme; Macnas's is the Bride of Frankenstein; and Spraoi's is the Vampire Legend. Expect plenty of blood, ghoulies, ghosties, zombies, bats, and other creepy characters. As well as the carriages, each company will also have a production out on the streets, among the audience, to compound the ghost-train atmosphere.

Spraoi will have a New Orleans-style funeral procession, with lots of jazz and dancing; Macnas will have a parade based on the nightmares of a fisherman; and Bui Bolg will be using the station stops to unleash a banshee-type diva who likes to lure opera-goers onto haunted train stations. It all sounds like the whistle-stop tour of the year.