Original: On 29 October 1873, the old Paris Opéra, known as the Théâtre de l'Académie Royale de Musique, which had been used since 1821, was destroyed by a fire which raged for 27 hours, leaving the whole of Paris in despair.
Simplified: On October 29, 1873, the old Paris Opéra, known as the Théâtre de l'Académie Royale de Musique, which had been used since 1821, was destroyed by a fire which burned for 27 hours.