The Theatre Royal de la Monnaie is one of the most famous opera houses in Europe. The first building was built in 1700 and has undergone many transformations. The current facade was built from the plans of the architect Eugène Simonis. To see an opera here, expect to pay at least 10 euros (the cheapest). You won't see much, but you'll enjoy the good acoustics.
In the restored Sint-Baafsplein you can find the Teatro Real in Ghent, which is notable for its facade. Above the entrance, Apollo and the Muses overlook the square, and at the top the goddess Harmony looks over it all. This is the municipal theater NTGent that although it is related to Ghent, it also has international works.
Antwerp Alexis Van Mechelen and E. Van Averbeke were in charge of the Antwerp Opera house in 1899. It opened in 1907, was decorated in neo-baroque style of Louis XVI. It has a capacity of 1006 spectators. Opera Ghent shares the same company, which is formed by orchestra, choir and technical team, founded in 1981. It was one of Antwerp's buildings that I like the most( including Grote Markt part that I found wonderful, hehe). So I recommend checking it out!! ;)