This is usually where the actors spend their time during shows when they’re not on stage.
There’s a table with a massive mirror, some stools, a piano, a couch, a cupboard, a massive throne, and usually also all the costumes that show (and frequently also previous shows) used.
This place gets recarpeted relatively frequently (read: about every 5 years), after which it naturally dies and has to be replaced again.
This is what it looked like after they re-did it and cleaned around 2014/15.
They also redid it in 2010 apparently.
This is what it looked like in October of 2009