Beltane is an ancient pagan fertility festival celebrating the coming of the Summer, or at least the end of the really bloody cold part of the year. Variations were current in many parts of Northern Europe at least until the middle of the 19th century, and may never have died out completely, but modern celebrations tend to build freely on the old rituals.

Edinburgh's Beltane celebrations are currently the world's largest, and Calton Hill now sees three hundred or so performers and up to twelve thousand punters gather on the 30th of April every year. Athletic hippies make human pyramids while clad in nothing but red paint and thongs, fire dancers spin their toys hypnotically, and dozens of drummers beat out mad rhythms through the night.

At the centre of the ritual is the coming of the May Queen, embodiment of Spring and femininity, and her male counterpart the Green Man, the same guy all those pubs are named after. He starts the night in the form of the Horned God, gnarled and weighted down with the baggage and overgrowth of the old year. At the climax of the night, he is ritually stripped of his excess vegetation to be reborn as the new Green Man, representing the shoots of new life that can flourish when the brash is cleared away. Fires are lit, from a single 'need-fire' started by friction, to burn away the old and superfluous - leaving what survives cleansed, revitalised and a bit warmer.

Up to this point, everything is straight out of recorded folklore. If that was all there was to it, though, it probably wouldn't be that much of a party. Records being patchy, and paganism being a living tradition, large parts of what happens on Calton Hill have been invented anew, sometimes every year. Many new elements have been added since the festival was revived twenty-two years ago, drawing on archetypes and ideas that our ancestors may or may not have been aware of. The resulting mishmash works well both as ritual and theatre.

The Goddess, the God and the fire all start on the Acropolis and then make their way round the hill with an entourage of drummers and White Warriors*, guardians of the goddess. They pass through the Fire Arch, entrance to the Otherworld, and visit each of the four elemental points, waking them as they go (each performs for ten minutes or so, going on for some time after the procession leaves). Then they have a run-in with the Reds*, nearly-nekkid forces of chaos, who generally piss around and show off with acrobatics and dancing, before they move on to the ritual exfoliation of the Green Man. Throughout all this there is other fun stuff happening in various parts of the hill, particularly the Acropolis and the nearby stage, so it's usually best not to even attempt to follow the procession all the way around. Ideally you want to be there with some friends who will keep you entertained while you're not in range of any performance - there's usually a lovely vibe in the crowd.

Hundreds of people, many of them not particularly pagan or even really hippies, devote countless hours of their time to this thing every year. A lot of that has to do with the community that's grown up around the festival, the skills you learn and the inhibitions you overcome when you get involved. It's also the best way to see it all - especially if you're one of the stewards, who typically get to see everything the procession passes.

This will be my third year being involved. I was a satyr-like creature in 2008, guarding the Fire Arch with a flaming sword, and I dressed in muslin with a big wavy cloth to represent the notoriously difficult-to-signify element of Air in 2009. I also took part in the Beltane Fire Society's other main festival, Samhuinn, last year, as one of the 'Valravn' - a half-raven spirit, representing inevitable death. This year I'm looking forward to making and controlling a giant puppet, with the Red Puppeteers.

All in all, Edinburgh's Beltane is a curious amalgam of folk festival and modern creativity, and a truly enormous community arts undertaking. For something that's theoretically all about a single night of the year, it seems to have a remarkably large effect on the social scene and character of the city.


*The Reds were known in the past as the Red Men, rather confusingly since so many of them were women; the Whites have been known as the White Women, or White Warrior Women, and I think this might be the first year they won't be wearing frocks. A great deal could be written about sex and gender at Beltane, but I think I won't.