The remains have been found of a theatre in London that preceded the Globe and the Rose theatres in staging William Shakespeare's plays.
Historians knew of the theatre known as The Curtain, in Shoreditch in east London, but were never exactly sure where it once stood.
The playhouse was home to Shakespeare's company - the Lord Chamberlain's Men. Shoreditch was a poor but vibrant district in Shakespeare's time.
Now, remains of walls forming the gallery and the yard within the venue have been discovered by archaeologists from Museum of London Archaeology.
The museum says it's one of the most important Shakespearean theatres in London and the preservation of its walls has been good.
The Curtain Theatre opened in 1577 close to London's first playhouse, The Theatre, and was one of a number of early theatres built outside the city's walls.
The venue took its name from a nearby street, Curtain Close.
It was the main arena for Shakespeare's plays between 1597 - 1599 until the Globe was completed in Southwark, but it is unclear what happened to the playhouse after that.
The site's owners, Plough Yard Development, plan to make the theatre central to their redevelopment plans.