As the Citizens Theatre in Glasgow celebrates its seventieth year of theatrical excess with a welter of activity that includes several high-profile shows and a BBC TV documentary, Blood and Glitter, set to be screened this week, a much less lauded but equally key influence on the Citz style and way of doing things is also being celebrated.

It was fifty years ago that that The Close, a 150-seat studio space in a former gambling club adjoining the Citz, opened its doors to a new world of experimental theatre. In the club-based theatre's short but colourful life between 1965 and 1973, The Close played host to some of the more outré contributions to the European art house canon in a uniquely underground environment which managed to circumnavigate the censorship imposed on live performance by the Lord Chamberlain up until 1968 when his role was abolished.

In its eight year existence, The Close may have began with productions of rarely seen curtain-raisers by Shaw, but there was also a controversial mask-based take on Faustus by American director Charles Marowitz and early sightings of work by Jean Genet and Marguerite Duras. Later there were double bills of Pinter, productions of Jack Gelber's drug-based play, The Connection, Heathcote Williams' counter-cultural classic, AC/DC, and a legendary all-male look at Genet's The Maids. The latter, directed by mime auteur Lindsay Kemp, featured a young Tim Curry sporting a corset he took with him when he played Frank N Furter in the original London production of The Rocky Horror Show.

The Close's club status also allowed the theatre's management to keep the bar open later than any Glasgow city centre pubs, thus providing a natural and necessary home for some of the Citz alumni's more flamboyant after hours excesses. If an anything goes attitude prevailed both onstage and off in the hothouse laboratory of The Close, once it burnt down, the same libertine spirit was taken onto the Citz's main stage which it would end up defining.

It is with this spirit that the Citz has programmed The Close Anniversary Season, a series of three shows performed in the theatre's now rarely used Circle Studio space, and which aim to recapture The Close's sense of daring and redefine it for a twenty-first century where safety all too often in art comes first.

“It was illicit,” current Citz artistic director Dominic Hill says of The Close, “and it felt like Glasgow's only gay club at the time. It was inspired by the Traverse, which had opened in Edinburgh two years before, and the desire to get something that was the equivalent of the Traverse on the west coast. At the time it existed it was vital in a lot of ways because there was nowhere else that was really like it.

“The Close had an underground subversive feel to it, which is something that's hard to find these days. There was a feeling that anyone could do anything, which was inspiring, and which eventually led to the founding of The Tron to fill the space that the Close left when it had gone. There's a line of theatrical legacy there that goes from the Traverse to the Close to the Tron and then later to everything that the Arches did.

“Once we realised it was the anniversary of The Close, we wanted to celebrate that and the influence it had on the Citz itself. We also wanted to do something in the Circle Studio, which we don't use much, but which isn't going to be around long, and to work with young directors who we already have a relationship with.”

For the latter, Hill has drafted in Debbie Hannan, who directed a remarkable staging of Dostoyevsky's Notes From Underground, Matthew Lenton of Vanishing Point, who are now cultural tenants at the Citz, and Gareth Nicholls, , who as the Citizens Main Stage Director in Residence oversaw a revival of Robert David MacDonald's adaptation of Gitta Sereny's book, Into That Darkness.”

The Close anniversary season begins with Hannan's production of English iconoclast Howard Barker's biblically-inspired look at the last days of Sodom, Lot and His God. This is followed by Lenton's Striptease and Out At Sea, a double bill of plays from the early 1960s by Polish absurdist Slavomir Mrozek. Completing the season will be Vanya, a contemporary response to Chekhov by Sam Holcroft, directed by Nicholls.

While the choice of plays was left to each director, Hill set down some parameters for each to work with.

“I said that they should either draw on the fact that the theatre was influenced by the classical repertoire,” says Hill, “that they should reflect the European nature of the repertoire, or that the work was very different or experimental in a way that you wouldn't necessarily put it onto a big stage, and I think we've covered all three of those bases.

“We also don't have a lot of money to do this, so while the actors and the directors are being paid, anything else they want has to be found from within the building. The important thing is to get the work on and for people to see it. That applies both to the Studio and to the main stage.”

This consciously Poor Theatre approach itself harks back to a can-do era of creativity which studio-based fringe theatre was sired on. As Hill and the Citz embrace a new era of DIY, he acknowledges too how much starved resources have changed things.

“We're living in an age now where there are hardly any studio theatres anymore,” he says. “There was a time in the 1970s when, not just fringe theatre, but studio theatres and regional theatres were a crucial part of the theatrical lifeblood of what was going on. A lot of that has gone now, and a theatre having a regular second space is not deemed to be as important as it once was. That has an effect on new work, and theatres without those spaces aren't able to stage work that's as experimental as they might like. When I think about studio theatres in Scotland, there’s really just the Traverse and ours, which we hardly ever use.”

Since arriving at the Citz, Hill's raison d'etre has been one of putting big plays onto the main stage, including works that might normally be seen in smaller spaces. While he admits to an ambivalence towards studio spaces in this way, he recognises the value they can bring to the development of new and experimental work.

With this in mind, while the Citz's Circle Studio will soon be demolished as a part of the theatre's ongoing multi-media development, it looks set to be replaced in the new building by a purpose-built 170 seat studio theatre. It's name, for the time being while in the planing stages, at least, is The Close.

“The legacy of The Close is the legacy of the Citz,” says Hill. “It's part of the creative thing that goes on here. All that energy that was channelled into the Citz after the Close's demise was so fruitful in everything that followed on the main stage, and that energy has permeated down into everything that's happened in the Citz over the last forty years and hopefully beyond.”

The Close Theatre Anniversary season runs at the Citizens Theatre, Glasgow, from October 3-November 7. Lot and His God, October 3-10; Slavomir Mrozek double bill – Striptease and Out At Sea, October 17-24; Vanya, October 31-November 7.