LAS VEGAS (AP) _ His imprint dominates the Las Vegas Strip and other gaming venues. But Tony Marnell says his latest $200 million fling, the expansion of his popular Rio Hotel Brazilian-themed resort, is his best yet.

``This ranks right at the top,'' Marnell said recently, taking a break from surveying crews working feverishly to put finishing touches on the Rio's new Masquerade Village.

Marnell heads the construction and design company behind some of the most famous names in casinos _ New York-New York, Bellagio, The Mirage, Excalibur, Caesars Palace, Treasure Island, Caesars hotels in Atlantic City and Lake Tahoe, Nev., to name a few.

His company, Marnell Corrao Associates Inc., is known as the world's largest designer and builder of resort hotel-casino properties, having built more than 55,000 rooms for the industry.

``He's been instrumental in a number of projects in Las Vegas,'' Scott Renner, a gaming analyst for Salomon Brothers, said of Marnell. ``You can't mention a new generation of developments in Las Vegas without mentioning his name, because he's had an influence on them. The Rio has provided him an outlet to express his penchant for quality.''

While he's just wrapped up construction on the unique $430 million New York-New York resort, and is busy helping build Bellagio, Mirage Resorts' $1.25 billion showplace hotel, Marnell's paying particular attention to the Rio.

The all-suites hotel opened here in 1990 with a single tower. Marnell took over the Rio's day-to-day operations 10 months later.

``It was not living up to its expectations,'' Marnell recalled, taking a break in Mama Marie's, a restaurant named after his mother. ``We thought we'd come in and run the day-to-day operations the way we'd planned.''

Beefing up food service, creating a carnival atmosphere and offering entertainment such as Tony Bennett, The Beach Boys and Donna Summer, the Rio has become one of the hottest properties in town.

Marnell also added a new 41-story tower, whose highlight, the $25 million Masquerade Show in the Sky, opens Friday night.

The additions are ``a natural extension of the Rio idea,'' Marnell said. ``It's centered around having fun, not just centered around gambling. Sometimes it's hard for casinos to think that way.''

The show is on the ground floor of the new tower, and will feature five giant floats, some weighing more than eight tons, running suspended on a 950-foot track, 13 feet above the casino floor.

The floats will parade through the casino every two hours and include 36 costumed performers and bungee-jumping acrobats. People will be picked from the crowd to join performers on the floats.

``It will be just like Fat Tuesday every two hours,'' said resort spokeswoman Chrisse White-Waddell, referring to the Mardi Gras themes.

The carnival is expected to enhance the Rio's strong reputation. The prestigious Zagat Survey of U.S. Hotels, Resorts and Spas has ranked the Rio No. 1 in the categories of Best Overall, Best Dining, Best Rooms and Best Service.

``We have always felt very strongly that the product the Rio offers in Las Vegas is at or near the top of anything in the market,'' Renner said in a telephone interview from his Tampa, Fla. office. ``In everything that we've seen it appears to me, and we are expecting, the new project will be very very successul, and will continue the tradition of quality they've established.''

With the new tower, Marnell, chairman and chief executive officer of Rio Hotel and Casino Inc., has given the resort 2,563 suites, making it the 13th largest hotel in the world.

Marnell, who holds 25 percent of Rio Hotel & Casino Inc., is the largest stockholder in the public company.

He and his associates are considering a new resort on 35 acres they own nearby. But that's taking a back seat until Friday's opening.

``Feb. 10, we'll begin thinking about the new project,'' he said, grinning.

Marnell, 48, has a background in architecture. But he says his success does not come from being a builder.

``Operationally, the gaming business is not a difficult business,'' he said. ``The gaming business is about people. The most successful operators are people who know about people.''