Look for more grandiose productions of opera in historically significant sites. The trend began last year in Egypt with a lavish presentation of Verdi's "Aida" at the Temple of Luxor, and plans are now in the works for a spectacular production of Verdi's early opera "Nabucco" set against the ancient walls of Jerusalem. Less definite schemes are afoot for more exotic (and expensive) productions, such as Puccini's "Turandot" in the great courtyard of the Forbidden City in Beijing in 1990, Bizet's "Carmen" in Seville in 1992 (as part of the World Columbian Exposition in Spain), Puccini's "Madama Butterfly" in Nagasaki, Japan--where it is set by the composer--and Saint-Saens' "Samson et Delila" in Ahskelon, Israel. The "Nabucco" production, set to open May 15, is costing upwards of $8 million, according to the producer, Michael Ecker. Ecker said the production's four alternating casts will include such singers as Ghena Dimitrova, Renato Bruson, Grace Bumbry and Ingvar Wixell. Michel Plasson will conduct the Royal Philharmonic orchestra of London.