Travellers to the suburbs on Waterloo Station can have no idea what is going on under their very feet and noses. Time travellers to the Underbelly in Cowgate, Edinburgh, during the festival, however, will know exactly what to expect in this extraordinary six-week rave-up called "Vault" in the dark and dank caves and alleys behind Platform One.
Perhaps that should be Platform One and three-quarters: one short visit to see Filter Theatre's electronic spattering of Macbeth, with a butch and brave lead performance by Ferdy Roberts, was enough to suggest a Hogwarts hootenanny of spells, flying sorcery and ghostly illusion.
Absolutely right for the play, of course, which is despatched in just 80 minutes by Roberts, Poppy Miller as a spell-binding Lady M and another five actor/musicians filling in the rest of the roles and messing around on the sound design apparatus of keyboards, synthesizers, percussion and anything else with bells on.
This carefully controlled "mess" - presented in collaboration with Tobacco Factory Theatres in Bristol - was a delightful surprise for the same company's deconstruction of Twelfth Night (with the Royal Shakespeare Company); here, it seems an almost conventionally appropriate tactic.
Appropriate, too, that a man who has no spur to prick the sides of his intent but vaulting ambition should be holed up in the underground Vaults, a comment in itself on his buried desires and certain failure. The rumbling of the trains is a peal of thunder, the fast exchange of questions after the murder of Duncan a whisper from the walls, the witches' incantation and the winding up of spells a carefully plotted aspect of the musical direction by composer Tom Haines.
The ingenuity, and poetry, of all this then begs another question: could not the performance have expanded in scale to the very depths and edges of this tunnelled, sewer-like environment? There was a fantastic "site-specific" Macbeth by Out of Joint some years ago, where we moved elsewhere for the banquet, rubbed our faces in the intimate confessions. Here, we might have journeyed to the blasted heath, or met the murderers on the road to kill Banquo.
Still, I've no complaints about the intensity of the performance, and perhaps it needs this compression, not dissimilar to that of Ian McKellen and Judi Dench's fabled close encounter in the Trevor Nunn production. One thing McKellen didn't do, though, was consult Brodie's Notes on the meaning of "To know my deed 'twere best not know myself…." Roberts no doubt feels, in the end, he's cabined and confined as well as truly cribbed, poor fellow.
Macbeth runs at the Vault Festival until 15 February 2015.