Construction has started on Alexandra Palace as part of a £26m restoration project to save its east wing.
The project will bring back the palace's Victorian theatre, which has been out of use for more than 80 years. The new theatre will have seating for up to 1,300 people when it opens late next year.
The refurbished East Court, set to be finished in 2018, will be a public space for exhibitions and other events under a glazed roof. There will also be a cafe, information centre, and ticket office.
Heritage specialists are working on the theatre, first built in 1875, in conjunction with construction firm Willmott Dixon, to help make sure as much of its character is retained as possible.
The Alexandra Park and Palace Charitable Trust (APPCT) is accepting donations to help fund the restoration (people can name a seat in the theatre), but most of the funding is coming from the Heritage Lottery Fund and Haringey Council.
The APPCT won £18.8m of lottery funding in 2015, and Haringey Council is giving £6.8m to the project.
Louise Stewart, chief executive of Alexandra Park & Palace Charitable Trust, said: "The public have waited so long to see this spectacular place, set high on a hill above north London, brought back to its original splendour and glory. It's unbelievably exciting to know that by next year we will have made such a big step forward."