Who needs Spider-Man and the Incredible Hulk when you have Harry Potter?

Amid speculation as to what Disney's announced $4-billion purchase of Marvel could mean to existing theme-park licenses, Universal Orlando today unveiled details for the Wizarding World of Harry Potter, a 20-acre addition to its Islands of Adventure.

The rights to the $265-million "theme park within a theme park" were secured from author J.K. Rowling in 2007, but NBC Universal has managed to keep information about the project a secret.

Wizarding World, set to open next spring, is expected to give Islands of Adventure a much-needed boost. Despite popular theme rides like Jurassic Park and the Spider-Man and Hulk roller coasters, attendance has suffered, Media Decoder reports. About 5.3 million people visited the park in 2008, compared to 17 million at the nearby Magic Kingdom.

And while Universal has a long-term licensing agreement east of the Mississippi for Marvel's best-known properties, the Disney deal raises the prospect of the superheroes appearing at parks in California, Asia and Europe -- and potentially weakening the appeal of Universal Orlando.

Wizarding World's centerpiece will be a 15-story Hogwarts School of Witchcraft and Wizardry, which is expected to contain a "robocoaster" ride system in which visitors are suspended from a robotic arm.

The park also will include replicas of Hogsmeade Village, Hagrid's Hut and the Forbidden Forest.