Squirrel Creek Lodge, an 18,000-square-foot former steakhouse in Littleton, looks a lot like any other event space used for corporate get-togethers or run-of-the-mill wedding parties.

But Squirrel Creek has hidden depths. Nearly every weekend, droves of people visit for racy parties where open-minded couples meet other open-minded couples looking to spice up their sex lives.

Many participants call it "the lifestyle," although it's also commonly known as swinging.

Owner Kendall Seifert said Squirrel Creek is the biggest venue of its kind in the nation.

Among other things, Squirrel Creek hosts Scarlet Ranch, a 50,000-member swingers club that Seifert started more than a decade ago, before selling it. Members and guests come to the facility not necessarily to have sex, but to "go out to a club without kids," he said. "No thumping music, no bar fights."

"I think there is less sex here than in the parking lot of the Stampede (nightclub) on any night," he said. "The allure is you possibly could go have sex, if you wanted" — but in one of Squirrel Creek's six downstairs playrooms, not the parking lot.

Members live along the Front Range, as well as in Texas, Florida, Arizona, California and plenty of other places. For a busy event, 1,500 or more people show up, Sei-fert said. Nearby businesses are tapped for additional parking. Area hotels offer special rates and shuttles to people who come for the bashes.

Think of it as a country club, Seifert said, where people might sunbathe without clothes, cheer on participants in a foam fiesta (the foam gets sprayed on people; clothing is optional), or just dance and flirt — and that's it — in a sexually charged environment.

"If you are 45, where do you go?" asked Seifert, 50, a wiry guy who describes himself as ultraconservative. "We have comedians. We do things."

During a recent tour of Squirrel Creek, with its long bar, huge kitchen and array of games, workers were seen cleaning up an indoor pool party from the night before — the inflatable pool had collapsed and blow-up pool toys were scattered around. Squirrel Creek hosts fashion shows, volleyball tournaments, dance parties and more, most of it taking place on weekends.

On weekdays, Squirrel Creek hosts corporate parties, serves dinner to members and entertains different groups that want the facility more for its space than its provocative weekend vibe.

Seifert said he started his first club in Evergreen because he was bored. The parties were a gas, he said, and things grew from there. (That club no longer exists.)

"I underestimated the market severely," he said, while seated on a Squirrel Creek patio that overlooks a big tepee, a volleyball court and a series of canopied beds on the property. "I had no idea."

"Way too boring"

Long before she got married, Emily Bitti knew monogamy wasn't for her. Good thing that her husband agreed.

For about a decade, the Broomfield pair have hit swingers clubs, attended meet-and-greet events at bars, booked vacations at adults-only resorts, and gone on dates with people other than their spouses.

Where some couples might dabble in partner swapping, it's a way of life for Bitti and her husband.

"I can't even imagine us being in a traditional marriage," said Bitti, an attractive 31-year-old who frequents the parties at Squirrel Creek. She owns kasidie.com, a social network for couples and singles who are looking to invigorate their sex lives. "It would be way too boring."

How prevalent is swinging? It's not something that is routinely tracked by academics with big budgets for data collection. The largest study, conducted in 2000 by Bellarmine University sociologists Curtis Bergstrand and Jennifer Blevins Williams, found that 84 percent of swingers are married couples or in relationships and had been together for a little more than 10 years.

Among swinging couples, marital happiness averaged 78.5 percent, compared with 64 percent of the general married population. Women on average are 31 when they embrace the lifestyle, while men are 35. Religious? Seventy-two percent belong to religious institutions, compared with 61 percent in the general population.

Michelle Golland, a Los Angeles sex therapist, said she thinks swinging is increasingly popular in part because of the importance couples place on having positive attitudes toward sex.

"We have a higher expectation for intimacy, for sex. We are healthier, stronger," she said. "I want to stay young and sexual in my heart. I want my husband to want me that way."

And swinging helps boost the sexual connection of some couples, she said.

"But this is not to solve a problem," she said, stressing that couples should be comfortable and happy with each other sexually before joining the lifestyle. "It's to experience something that is hot, erotic, interesting, and keeps your sexual life together alive and growing."

Bitti said the lifestyle includes emissaries from nearly every demographic — cops, teachers, CEOs and the rest of us. And where the caricatured swinger is a potbellied, middle-aged dolt out for some easy action, the reality is less unsettling, she said. Adults of all ages participate, looking good matters, and players tend to have good jobs and fertile imaginations.

She prefers the term "sexually social" to swinger. It seems more approachable and friendly, she said.

Like other swingers, Bitti calls people who are outside of the lifestyle "vanilla" and laments that her multiflavored approach to relationships remains relatively subterranean.

"We are just about being who we are, but we are all living in the closet. People are worried about losing their jobs, their kids," said Bitti, who along with her husband is so enthusiastic about the lifestyle that they are one of the lead couples on a Playboy Channel show called "Swing."

Bitti is so very out about the lifestyle, in part, to help drag it closer to the mainstream.

The stigmas still thrive, even in Colorado, but they appear to be eroding, said Denver sex therapist Neil Cannon.

"There are more people who are willing to find more creative solutions to how to make their marriage or relationship work," he said. "It's hard for some people to get all of their needs met in one relationship. In America, everybody assumes we are monogamous and that's the only way to live."

Exploring the lifestyle is not for everybody, he said. For one thing, concerns about sexually transmitted diseases alarm many people. Practicing what Cannon calls "safer sex" is simply imperative. Also, jealousy renders many people incapable of letting a spouse run off with others for romps between the sheets.

Those who succeed, he said, tend to bask in their partner's joy, regardless of whether it bubbles up from a career triumph or a sexual escapade with another adult.

And many of those who thrive in the lifestyle appreciate places such as Squirrel Creek.

In the past, Cannon said, "there were lots of places, but they were small, in people's homes. I think it's important to remember that markets make businesses — businesses don't make markets. There are people who want to do this."

Of his swinging clients, who range in age from their early 20s through their 60s, most are well-educated and intelligent and run the spectrum in terms of their appearance, from muscle-threaded jocks to waif accountants.

Bitti said she has seen wary tip-toes into swinging build stronger relationships, and she has seen it rip apart couples.

For her, monogamy was never an option — she doesn't want tiny steps from one lifestyle to another and doesn't want to worry about how a more free-ranging approach to sex might mess with her domestic life.

"We all have these thoughts. 'Ooh, I have a connection with that person.' And now I can explore it, and it's not going to threaten my marriage," she said. "It's blowing away those cobwebs in your sex life. I have a boyfriend, and I met his wife for lunch yesterday."