Built opposite the spa in the alignment of the park's central walkway, the original casino, designed by architect Charles Badger, was inaugurated on 2nd July, 1865.
Its main façade, which opens directly onto the park, is decorated with caryatids representing the four seasons. On the side facing the park, the Casino included a vast ballroom, flanked by a conversation room for ladies and a reading room reserved for gentlemen; on the side facing the street, there was an 820-seat theatre, with gaming rooms (Jeu des Petits Chevaux and billiards) on either side.
A new agreement, signed in 1898 between the French State and the Compagnie Fermière that managed the spa resort, required the latter to undertake major extension work. Architects Charles Le Coeur and Lucien Woog built a 1,400-seat opera house on the western side, along with a vast room serving as both opera house foyer and banquet hall, and a restaurant on the eastern side. The former theatre was converted into a gaming hall, although gambling was not authorised until 1907.
In 1988, the building was taken over by the City, which restored the opera house and converted the casino into a convention centre – the whole complex being inaugurated in 1995.