Orange County, Calif., is generally associated with urban sprawl, not magnificent parklands — but a massive new land deal could help change that. The 4,738-acre “County Great Park” will be bigger than New York’s Central Park and San Francisco’s Golden Gate Park put together, and will include riparian corridors, botanical gardens, sports and educational facilities, and plenty of green space. The park will rise on the site of the former El Toro Marine Corps Air Station, which shut down in 1999. County approval for the park came this month, following years of bitter battle between those who wanted the open space and those who wanted to build a new airport on the site. Many now hope that the park will become a model for what to do with other U.S. military bases closed in the 1990s.