There's a nervous energy reminiscent of a high school dance in the main ballroom at the Denver Turnverein on a Sunday night. About a dozen people are warming up for their dance lesson, including 52-year-old Anna Vela.

"I've never been here. So I don't know how this works," Vela tells the woman at reception -- Vela's also new to West Coast Swing. 

As the sun sets through the big windows, the room dims and nerves settle. An hour later, the dance floor gradually fills with swinging dancers of all levels. 

This is how most evenings start at the Denver dance hall, which has become the Colorado hub for social dance over the past few decades. But 150 years ago, the Denver Turnverein wasn't about dancing. 

The Denver Turnverein's origins

"Turn-verein means gymnastic club, essentially," the club's vice president, Ted Simmons, says, who's an an avid ballroom dancer and Lindy Hopper.

Simmons has been researching the club's history ahead of its 150-year anniversary.

He explains that the club started in the back of a downtown Denver bakery in 1865. German immigrants gathered to practice  gymnastics behind the building. Eventually, they applied to be an official gymnastics club -- or "turnverein" -- through the American Turners, a national German cultural association. 

Dance made its first appearance the following year.

"Really the way that they got their funding, was by starting a masquerade ball," Simmons says.

While these parties helped pay the bills, the focus remained on gymnastics and fitness -- even after the club moved into its current home in the 1920s, a stucco building that is easy to miss if you aren't looking for it. Back then, tumblers had to dodge large chandeliers in the main room upstairs, which still hang from the club's high ceiling.

Tango transformed the club

In the late 1990s, Tango Colorado set up shop at the Denver Turnverein. That turned out to be a pivotal moment for the club.

Brian Dunn remembers his first visit to the Turnverein in 1997. He came to learn the Argentine tango. 

"I showed up -- there were about 16 people -- I looked around and I was tremendously nervous," Dunn says. "I had had a couple of tango lessons. So I asked somebody to dance, apologized and just kept coming back."

Now, he teaches the Argentine tango, and says he wants every student to feel welcome.

"We want to make you the most popular social tango dancers for a thousand miles around," Dunn says. "This is a great place to do that because there's generally an atmosphere here of everybody wanting that. Everyone wants more fun people to dance with."

The tango lessons caught on, and word spread that the Denver Turnverein was the go-to destination for tango lovers on Tuesday nights. Shortly after, the club expanded its curriculum, adding ballroom, salsa, country western dance, Lindy Hop and West Coast Swing. 

Instant community

The Denver Turnverein has about 1,200 members and Ricardo Newton is among them.

The self-proclaimed "tango extraordinaire" started coming to the Turnverein more than 15 years ago.

"I hadn't a clue what dance was all about," Newton says.

Now, he rarely misses a milonga. 

"It's the ambience of the building itself,"Newton says. "It's the characteristic. It's the dance floor. It's the people. It's the music and it's the camaraderie that we all share."

And Newton plans on dancing another 15 or more years at the Denver Turnverein.

"Wild horses couldn't keep me away," he says.

Vela understands this now. By the end of the night, she's exchanging numbers with other dancers and showing off what she's learned in the last hour. 

"Let's see, you start this way," Vela says as she demonstrates the basic West Coast Swing step.

Her face is flushed as she gushes about how much fun she's had learning to dance. And she promises she'll return to the Denver Turnverein for more dancing.

This Saturday, the Denver Turnverein celebrates 150 years with an open house and masquerade ball.