Shakespeare experts have hailed the "thrilling" discovery of remains of the predecessor to The Globe theatre.
Plays including Henry V were first performed at The Curtain Theatre - immortalised in that play as "this wooden O" - and Romeo And Juliet might also have premiered there.
Parts of the playhouse's yard and gallery walls were excavated in Shoreditch, east London, by the Museum of London Archaeology (Mola) as part of regeneration works.
Parts of the Curtain Theatre being excavated in Shoreditch, east London
It is hoped the site could be opened to the public and plays could be staged there in the future.
Royal Shakespeare Company artistic director Michael Boyd said: "It is inspiring that the Museum of London has unearthed the foundations of The Curtain Theatre.
"I look forward to touching the mud and stone, if not wood, and feeling the presence of that space where Shakespeare's early work, including the histories, made such a lasting impact."
Actor Eddie Redmayne, who won last year's Critics' Circle Theatre Awards for Best Shakespearean Performance for his Richard II role at the Donmar Warehouse, said: "The discovery of The Curtain in Shoreditch is a thrilling prospect particularly in this year of the World Shakespeare Festival.
"With The Globe and The Rose having helped add such cultural vibrancy to Southwark, I'm excited to see what the exploration of this exceptional site will unearth and bring to this already brilliant area of the capital."
The Curtain, which opened in 1577, was operated by theatre manager James Burbage and was home to Shakespeare's Company, the Lord Chamberlain's Men, before The Globe opened. It was the main venue for the Bard's plays from 1597 to 1599.
It disappeared from historical records in 1622 but could have remained in use until the outbreak of the Civil War, 20 years later.
Plough Yard Developments, which owns the site, is planning to make The Curtain central to its redevelopment of the area.
Further excavations are to take place of the remains, three metres below ground.
An artists impression of what the site might look like following regeneration works
A spokesman for the developers said: "This is one of the most significant Shakespearean discoveries of recent years. Although The Curtain was known to have been in the area, its exact location was a mystery.
"The quality of the remains found is remarkable and we are looking forward to working with Mola, local community and Shakespearean experts to develop plans that will give the public access to the theatre remains as part of a new development."
He added that there was a 50/50 chance that The Curtain, named after nearby Curtain Close, was where Romeo And Juliet was first performed.
Kim Stabler, archaeology adviser at English Heritage, said: "This is an outstanding site - and a fortuitous find in the year of the worldwide celebration of Shakespeare.
"Developer-led archaeology, investigating and recording a site before any construction begins, has undoubtedly enriched our understanding of our towns and cities. A sensitive and creative public presentation of these remains would be a fantastic addition to telling the constantly unfolding story of London."
Neil Constable, chief executive of Shakespeare's Globe, said: "The find is another wonderful opportunity to further our understanding of Shakespeare's theatres."
Chris Thomas, from Mola, said: "This is a fantastic site which gives us unique insight into early Shakespearean theatres. We are delighted that Plough Yard Developments plan to preserve the remains in place and open them up to the public as there are few similar sites across the UK."
A planning application for the redeveloped site is to be made this summer. Proposals for the site are going on display in Shoreditch on Friday.
