The Opéra Royal is one of the finest 18th-century theatres in Europe, tucked into the north wing of the palace and often missed by visitors who don't know it's there. Designed by Ange-Jacques Gabriel and completed in 1770 after decades of planning and delay, it was inaugurated for the wedding celebrations of Louis XVI and Marie Antoinette with a production of Lully's Persée.
The interior is a tour de force of trompe l'oeil: what looks like marble is painted wood, what appears to be carved stone is sculpted papier-mâché — a practical solution that also gave the theatre its remarkable acoustics. The oval auditorium seats around 700 and was designed so that the stalls could be floored over to create a ballroom at the same level as the stage.
The theatre is still used for performances. The Centre de musique baroque de Versailles programs it regularly, and visiting on a performance evening — Baroque opera, court music, period-instrument recitals — is one of the best ways to experience the palace outside tourist hours. Check the schedule before you visit.