Al Seib / Los Angeles TimesConfetti fills the early-morning sky as enthusiasts walk through the front gate to The Wizarding World of Harry Potter attraction that opened to the public Thursday.

LOS ANGELES — Six decades ago, Walt Disney opened what would become the nation’s prototypical theme park, a fantasy land built around Sleeping Beauty Castle, a 77-foot-tall marvel inspired by the classic fairy tale and Disney’s soon-to-be animated film.

On Thursday, Universal Studios Hollywood, long considered second tier compared with its more popular rival, threw open the gates to its own fantasy fortress: a 200-foot-tall Hogwarts castle, inspired by the modern international literary sensation Harry Potter.

In the hyper-competitive world of Southern California theme parks, it’s game on.

Universal Studios Hollywood’s new Wizarding World of Harry Potter, part of a $1.6 billion upgrade, presents the first serious challenge to the preeminence of Disneyland, which is undergoing about $1 billion in upgrades of its own — a 14-acre expansion based on the “Star Wars” franchise.

“The product offerings at Universal are such a high quality that they are at the same level as Disney in many aspects,” said Dennis Speigel, president of International Theme Park Services in Cincinnati.

As Thursday dawned, fog machines pumped out a gray swirl around the archway entrance to what is predicted to be Universal Studios Hollywood’s most popular attraction ever.

Some visitors reported opening-day glitches, which park officials had hoped to avoid by conducting weeks of technical rehearsals with random groups of customers.

The complex 3D-HD dark ride, called Harry Potter and the Forbidden Journey, broke down for a few minutes when Sarah Mahony was riding.

The projection in front of her froze and then went black, but the seat kept moving as a recorded voice repeated: “Please stay in your seats, everything is all right.” Mahony, 20, said she was nervous, but the ride quickly started working again.

Inside the 6-acre interpretation of Hogsmeade village from J.K. Rowling’s seven “Harry Potter” books and the eight Warner Bros. films that followed, the varied architecture suggests a place that grew over time, complete with rust and other signs of faux age. Props from the films are sprinkled throughout. Moaning Myrtle can be heard in the bathrooms.

This kind of immersive storytelling and attention to detail not only brings the park into Disney’s league, experts said, but the estimated $500 million attraction also could become such a tour de force that it cuts into Disneyland’s business this summer.

Andrew Dinh, who was roaming the Potter land with his 5-year-old daughter, Taytum, had already spent about $500 on items including robes, wands, shirts and temporary tattoos.

“It’s both for her and me,” admitted Dinh, 36, a Riverside County deputy sheriff.

When a similar Harry Potter world opened in 2010 at Universal’s Islands of Adventure theme park in Orlando, Florida, attendance jumped 30 percent at that park that year while visitation numbers at Disney’s Magic Kingdom nearby dropped 1.5 percent.

“Disney might take a small dip this year because local people will decide to go to see Harry Potter,” said Gary Goddard, a theme park designer who has worked for both NBCUniversal and Walt Disney Co.

But Disneyland is not sitting idly on the sidelines. The park has started construction on the 14-acre expansion based on the blockbuster “Star Wars” films. A completion date has yet to be announced.

“For 60 years, Disney has led the industry in creating immersive theme park experiences, and we continue to raise the bar during one of the largest expansions in Disney Parks history with Star Wars-themed lands at both Disneyland and Walt Disney World,” Disneyland spokeswoman Suzi Brown said.

Strictly by the numbers, Disneyland is packed with more attractions and draws more than twice as many visitors as Universal Studios Hollywood.

But Universal Studios Hollywood’s attendance has been growing faster than Disneyland’s, and the L.A. park has been adding new attractions at a greater pace.

Theme parks refuse to divulge numbers, but an annual report by Los Angeles engineering firm Aecom and the Themed Entertainment Association trade group estimated that Disneyland hosted 16.8 million visitors in 2014, a 3.5 percent increase over the previous year. Universal Studios Hollywood welcomed 6.8 million visitors, an 11 percent increase over the previous year, the study said.

The rapid attendance growth comes courtesy of several big-ticket attractions that Universal Studios Hollywood has added in the last four years.

In 2012, Universal Studios Hollywood opened Transformers: the Ride 3D, followed in 2014 by the Despicable Me Minion Mayhem ride and Super Silly Fun Land. The park launched Fast and Furious: Supercharged last year as well as Springfield, a city block of eateries inspired by the fictional town in the TV show “The Simpsons.”

Just in time to draw vacationers this summer, Universal Studios Hollywood plans to open a permanent haunted maze based on the AMC series “The Walking Dead.”

Although several attractions and parades have been overhauled in the last few years, Disneyland hasn’t built a major ride from scratch since it added the interactive Buzz Lightyear Astro Blasters in 2005.

Disneyland has retooled several attractions to appeal to fans of “Star Wars,” acquired by Disney along with Lucasfilm for $4 billion in 2012. An underused area in the Innovations building of Tomorrowland has been converted into Star Wars Launch Bay, a hall where parkgoers can play “Star Wars” video games, buy merchandise and meet costumed characters from the films.