Did you ever wonder who walks the dark pathways behind the locked gates of the Museum Gardens at night? Did you ever imagine there was a hidden other world existing just a dream away?

Now, as a centrepiece of the Illuminating York Festival, York Theatre Royal Youth Theatre will take you on a magical journey to answer these questions when the company presents Keys To The Kingdom from this evening until November 3 at 7pm and 8pm.

For the first time, the Museum Gardens will reveal its greatest secret and invite you to be part of "one of the most mysterious and unique events ever witnessed in York". Join the secret revellers at a celebration that never makes the headlines, a performance that exists between dusk and dawn, between dreaming and waking.

This production, written by Sheffield writer Richard Hurford and directed by Owen CalvertLyons and Julian Ollive, is produced in conjunction with York Museums Trust, and as a key part of Illuminating York it aims to promote the city's contemporary culture after dark.

Commissioned for this site by York Theatre Royal, The Keys To The Kingdom will be a 45-minute piece of promenade theatre that takes the audience around the gardens.

It will be performed on alternate nights by two casts of more than 20 performers, aged 14 to 16.

"From the outset, we felt it was vital to walk around site with Richard Hurford, choosing spaces that spoke to us as the writer and directors, so that it would become a piece that could not be housed anywhere but the Museum Gardens, " says Owen.

"The play plays on the mythology of the park being somewhere that something naughty or mischievous happens at night."

No, there will not be sordid occurrences. "Instead you'll meet three different guilds that form part of the invisible world of York, the Brick Leaners, the Earth Proppers and the Sky Blowers.

The premise is that the people of York are being invited into this world for the first time, " says Julian.

"This was very much Richard's idea. He says the three unseen guilds are holding the fabric of York together, and each evening people of the visible world are invited to celebrate the uncelebrated people of the city, without ever saying specifically who they are.

"The play offers a message about regeneration and an ecological message about looking after the world we live in. The unseen world is saying you need to come together to look after your world and the regeneration of your city."

  • Tickets: £3 on 01904 623568 or www.yorktheatreroyal.co.uk

Illuminating York 2007

Other activities include late-night opening at York Art Gallery and Café from October 29 to November 2, from 6pm to 8pm. Events include Timed Memory, a sound installation by composer and sound artist Angie Atmadjaja.

Evoke by Usman Haque is an interactive projection that will light up York Minster 's western facade, with members of the public using their own voices to create colourful light patterns that emerge at the building's foundations and soar up towards the sky.

Inspire features performances of contemporary music, dance, drama and literature in some of York's ancient buildings, all in one night - November 2, 6pm to 9pm.

Recovered Light is an artwork created by three New York artists and projected on to the Minster during illuminating York last year. Now it's visible up close and personal inside the cathedral.

Lux is a trail of 12 light-based artworks by recent graduates from York St John University in Gillygate, from October 26 to November 3, 5-8pm.

Full details of the festival can be found at www.illuminatingyork.org.uk