Sheltered by the looming presence of Southwark Bridge, a blue plaque on a modest doorway is the only hint of the treasure that lies in the basement of the Rose Court office building. Set back from the river, the unassuming entrance is not easy to find. You need to take a side road back from the bustle of the river-front by Shakespeare’s Globe and follow the chalk arrows down Park Street, provided they haven’t been erased by the rain. Then you step into the gloom of the foyer, and beyond that into an intimate theatrical space with a wooden floor, an ad hoc arrangement of chairs, and a mysterious, roughly circular expanse lit by red lights. You are now standing in the Rose Theatre, the first Elizabethan theatre built on Bankside in the year 1587, the theatre of Christopher Marlowe, William Shakespeare and Thomas Kyd.

The fragile remains are cared for by the volunteer-staffed Rose Theatre Trust, who are engaged simultaneously in a daunting search for funding to preserve the Elizabethan remains and the production of well-received plays. Summer 2011 saw their production of Othello extended due to demand, while their production of Henry VI Part 1 earlier in the year received a number of nominations in the Off West End Theatre Awards, the Offies.

It’s a cosy setting for a theatrical performance, with audience and performers up close and personal. The facilities are basic. Winter playgoers are advised to bring a blanket. But, rest assured, you can use the toilets in Shakespeare’s Globe, just around the corner.

With the rebuilding of Shakespeare’s Globe in 1997, this area of Bankside reclaimed its theatrical heritage and something of its rambunctious past. For in Elizabethan times, Southwark, the Soho of its day, was an area full of all manner of scandalous entertainment. Beyond the jurisdiction of the dour City of London authorities, the district was home to everything from inns to bear-baiting rings, gambling dens, brothels and the latest subversive innovation, the playhouse.

Theatre impresario and entrepeneur Philip Henslowe, who also owned a brothel, opened the Rose Theatre with his partner John Cholmley in 1587. Home to the Lord Admiral’s Men under the patronage of Charles Howard, Lord Howard of Effingham, the Rose Theatre staged such greats of English theatre as Marlowe’s Tamburlaine, Shakespeare’s Henry VI Part 1 and Kyd’s Spanish Tragedy before an audience of some 2,500 people. Modern calculations suggest 700 groundlings could cram into the space in front of the stage, paying a penny for the privilege. Elizabethan audiences were clearly far less demanding when it came to personal space than today’s.

Archaeologists had long known the theatre was there, but it wasn’t until Southbridge House was demolished in 1988 that they had the chance to see for themselves. Miraculously, the various buildings that had stood on the site over the centuries had managed to avoid seriously damaging the remains, thereby giving the archaeologists from the Museum of London an unexpected bonanza. The Rose Theatre was built on reclaimed land, and the moist conditions preserved the remains to a significant degree. The excavations covered two-thirds of the site, enough to build up a clear picture of an Elizabethan playhouse and influence the re-building of Shakespeare’s Globe, just around the corner.

The excavations took place in the full glare of publicity, as leading names from London’s theatrical world campaigned to save the site, and crowds gathered to watch the dig. Just weeks before his death, Sir Laurence Olivier recorded a speech in support of the campaign, ending with a rousing “Cry God for Harry, England and The Rose!”

It’s a cry that needs to be remembered. The remains of The Rose, upon whose boards Shakespeare and Marlowe trod, are fragile, and need to be preserved before they are lost forever.