The Mile High City is living up to its name. And I'm talking about the city's attitude, not its altitude.
If you're over 21 years of age, you can get as high as a kite in Denver, and it's all perfectly legal.
So cannabis - or marijuana, or weed, or pot, whatever name you call it by - is flourishing.
What we're witnessing in Colorado is the birth of an industry. Here they call it the Green Rush.
Like the Gold Rush era, thousands of people are flocking to Colorado. Tens of millions of dollars are at stake. Fortunes will be won and lost.
It's the greatest experiment in US drugs policy since the abolition of prohibition in 1933.
There are parts of the city that smell different. The "grow factories" where the cannabis plants are nurtured are high-tech labs, but the wafting odours permeate whole city blocks.
In Colorado, a whole section of society - everyone who smokes marijuana - is emerging blinking into the sunshine of legality.
They're adults and they're consuming a product arguably less dangerous than alcohol or tobacco.
What's not to like?
Well, drive towards the Rocky Mountain National Park and visit the addiction clinics for teenagers. Struggling youngsters are trying to put their lives back together. Many are desperate.
Aaron is a reformed cannabis user who runs one of these clinics. He is visibly furious with the change in the law.
The clinic has a growing waiting list and Aaron insists it is a disaster for the kids.
Now they have easier access to it than ever before. The teenagers steal it from parents who no longer have any need to hide their supply of legal marijuana.
Kids who should be alert at school are now stoned. Developing brains are impaired.
The parenting of teenagers has just become a whole lot more difficult. It's not so easy to draw a line. You can guess how the conversation goes:
"You're only 15 years old - no dope."
"But, Mom, Colorado says smoking weed is fine. It's legal. So why can't I enjoy it too?"
So even as the cannabis industry thrives, even as many adults celebrate a famous legal victory over America's discredited drug laws, there are plenty of people who believe that Colorado's experiment is just that - an experiment we should observe and study, not one we should rush to follow.