Houston's flagging civic pride will get a boost this weekend when the city's $72-million opera house opens. The Gus S. Wortham Theater Center, an arched red granite structure in the heart of the downtown district, is the first major U.S. opera house to open since the completion of the Kennedy Center in Washington 16 years ago. The Wortham's grand opening will be heralded with a stage production by Emmy Award-winning producer George Stevens Jr. Details of the production have been kept a closely guarded secret. Next year's season will include the world premiere of John Adams' opera "Nixon in China." Private donations paid for the structure, despite a downturn in oil prices that has drained jobs and money from the nation's fourth-largest city.