LAS VEGAS — I knew up front what to expect when I walked into the Jubilee! Theater at Bally's Las Vegas.

And I mean "up front."

No one younger than 18 is allowed in, and there's a reason. For more than 20 years, some of the best showgirls in Vegas have sashayed in front of these million-dollar sets wearing little more than sequins and smiles.

So you know from the get-go that some of the showgirls will be topless. But I guess I didn't really know what topless meant until it almost hit me in the head.

And I mean in the head.

She drops from the ceiling on a platform, right over the audience at the beginning of the show. I wasn't sure the older woman sitting next to me had noticed, so I nudged the grandma, and we both looked up and went, "Ohhhhh," at the topless Amazon drenched in crystals and spotlight standing above us.

She was stunning.

If not for my magpie fascination with shiny things, this would have been the tale of two shows — Donn Arden's "Jubilee!" one of the longest-running shows on the Strip, and "Ka," part of the Cirque du Soleil monster that's gobbling up Las Vegas.

I saw Cirque one night, "Jubilee!" the next.

High tech vs. high heels.

Kinda kooky vs. kinda campy.

At "Ka," the newest of four Cirque shows in permanent residence on the Strip, acrobats and martial artists leap and bound and fling themselves through the air with such gleeful abandon that I found myself praying for their safety. Praying, that is, when I could catch my breath.

Cirque is a wild ride from the moment you walk into the theater lobby at the MGM Grand and a ticket taker/warrior wearing a sword zaps your ticket with a scanner.

The stadium built just for this show is a dark and moody world. It's like a "Lord of the Rings" set or the inside of some crazy factory with all its steely innards exposed. Loud clanking, like giant hammers striking steel, fills the air as the audience arrives, and New Age-orchestral music rolls through like thunder.

As you watch the show you sense the social commentary. And if I'd taken time before to read the program about this "many-layered narrative" following the journey of a pair of twins, I would have learned that it has something to do with fire. But I lost that among all the gymnasts and giant puppets, and when the monstrous stage rises on end like a wall.

You had to be there. The Cirque experience is one of those once-in-a-lifetime shows, which explains the packed theaters every night.

Yet another Vegas-based show will open later this year at the Mirage, replacing, sadly, Siegfried & Roy. The new show is an homage to the Beatles, more eye candy for the increasingly sophisticated and wealthy Vegas visitor who doesn't come to Vegas just to play the nickel slots anymore.

But I'm neither sophisticate nor theater critic. And I have to say that as a fan of Fred and Ginger, Judy and Gene, I prefer my Vegas entertainment old-school.

Straight up. With a twist.

Few things are more intimidating for a woman than to meet a Vegas showgirl.

Or so I dreaded as I headed to the Jubilee! Theater for a backstage tour. It's the only behind-the-scenes tour of anything I found on the Strip.

Our guide was statuesque Holly Haynick-Dean, a friendly 26-year-old brunette with a degree in fine arts and a lifelong desire to dance.

She has been a showgirl for three years, and "Jubilee!" "is my first, like, huge, huge job," she said.

"I'm really proud to be a showgirl in this show, especially because it is true to what a showgirl was and used to be."

I liked her instantly.

Holly wore a sequined hot-pink costume with flesh-colored fishnets, gold dance shoes and rhinestones around her neck.

Her lips matched her costume and her eyelashes stood out to there. That's the showgirl look. Huge lashes, big lips. Very drag. The girls do their own makeup.

Holly led our group onto the stage, the closest I will ever come to commanding a Vegas spotlight. From up there the theater looked huge, 15 stories tall from the orchestra pit to the roof. Holly told me later that she can see people in the audience when she's dancing.

"Sometimes there's people sleeping, talking on the phone. People don't think you can see them, but that's what I tell them on the tour: 'I can see everything you do.' "

The proscenium arch soars 75 feet high over the front of the stage, "one of the reasons we use such tall dancers in the show," she said.

Women have to be at least 5- feet-8 to be a showgirl; the men 6 feet to be a showboy. (They really call them that.) The women look much taller because they dance in shoes with 3-inch heels braced underneath with metal so they don't break off during the dancing. The shoes also have rubber soles to prevent falls.

"And we wear insoles in our shoes, for padding," Holly said. "Being on the balls of your feet really takes a toll on them."

Showgirl and showboy feet take quite a pounding. Twelve 90-minute shows a week, every day but Friday. More than 600 shows a year.

As she cautioned everyone against taking pictures in the basement of the theater, Holly led us down a steep hill of concrete steps. Twenty, forty. It seemed like a hundred steps as we clopped down in our sneakers, sandals and flip-flops.

"These stairs are what all the performers and singers have to climb up and down between every single number," said Holly, who makes the trip at least 16 times every show.

"Do we fall down the stairs? Yes, we fall down the stairs all the time. Usually it's just a little trip. That's why it helps to hold the handrails.

"I'm not sure who designed a theater with the dressing rooms in the basement."

The 90-minute show, with no intermission, has changed little over the years, Holly said. I found out later what that entails. Lots of songs I knew, such as Irving Berlin's "A Pretty Girl Is Like a Melody." Pretty dancing, like an elegant pas de deux against a starry backdrop to "Smoke Gets in Your Eyes."

And pure camp, as in a Samson and Delilah number with guys in G-strings and my favorite lyric of the show: "She's got the hots for a guy named Sam."

"Jubilee!" is kind of like your neighborhood high school show, only with better singing, dancing, costumes and sets.

And bare breasts, which, as my brother-in-law had sworn, you aren't even really aware of after the first two or three songs. The novelty wears off quickly. (At least it did for me. I can't vouch for the group of twentysomething, thirtysomething guys sitting with big grins close to the stage.)

"I think that's one of the things that keeps our show going, because we haven't really modernized it," Holly said. "We kept it in the same Vegas, old-school genre, and we haven't made it into the new rock music, crash dancing, things like that, which is what a lot of the new shows here are. There are a lot of young adults who come here, and they want that type of show, but our show appeals to 18-year-olds and 90-year-olds."

I can vouch for that from my row with middle-age Japanese tourists on my left and a group of older women on my right.

Apparently more popular with the public than even scantily dressed dancers is the scene where the Titanic sinks, right on stage, sending more than 2,000 gallons of water cascading across the stage. "It's very real-looking," Holly said, standing next to the giant ship hulking silently in the basement. "It's an actual set change that's happening right before your eyes."

As she led us down a hall toward the costume closets, one man asked, "What's your age when you call it quits?"

Holly smiled. "In the '70s and '80s, dancers were done at 25, 26. Now, because I think people have learned to eat healthy and take care of their bodies and not starve themselves and not smoke, drink and do drugs, we've been able to stretch our dance careers out," she said.

"What's the oldest one?" persisted the man, pushing 65 if a day.

"In this show? 49."