(Besides the legal weed 
)
I’m going to Denver for the Great American Beer Festival! Long story short, I’m going to be on my own with nothing to do for one day (a Friday). I won’t have a car, so try to keep it to downtown and other places easily reached by train. My brother, who lives out there, hasn’t come up with anything yet, but I’m sure my fellow dopers know of some things that I must see (or at least enough to keep me out of trouble for an afternoon).
Their downtown is about five blocks long and two blocks deep. You won’t get lost. Denver is a magnet for a real specific type of panhandler: Young, able-bodied, reeking of college and middle-class privilege, and super-whiney when you say no. I imagine they predate pot legalization, but that can’t have made it any better.
Yes, I remember as a kid how we saw Denver coming up on the horizon then, suddenly, just a few moments later we were dag-smack in the middle of it without having gone very far. It actually hadn’t been “on the horizon”, it was just a city in miniature. The “skyscrapers” were half as tall and half as wide as a normal skyscraper and all the other buildings were scaled down by half to match.
I question what the intent of this bit of subterfuge was. It’s like the town was founded by the Wizard of Oz.
Still better than downtown Portland.
US mint is a fun twenty minutes for free, I like the random pianos on the street.
I really like Denver and Colorado, but I’m used to driving, so my advice is limited.
Well, one thing you can avoid doing is to look for Mork. He no longer lives in Denver.
The Rockies are at home, with games against the Pirates and the Dodgers. They’re also so deep in the cellar that you can probably get a ticket real cheap.
The zoo’s pretty nice.
I highly recommend taking the free tour at Stranahan’s, if you like whiskey. It’s definitely best to call ahead or use their website to reserve a place in the daily (except Tuesday) tours.
ETA: admittedly, I’m not sure that a tour of a whiskey distillery (with concluding free tasting) qualifies as “keeping out of trouble.” 
He never did - it was Boulder, not Denver.
As for the OP, sorry no help. My SIL lives in Colo. Spgs. and we often head up to Denver for a day when we are out there to visit, but we usually drive and I don’t know my way around well enough to know where things are and how to get there on foot.
The bus still goes to Boulder, right? Might make a nice day trip.
Or, take a cab down to East Colfax.
j/k
Mmmmmmm…hookerlicious…
The Denver Museum of Nature and Science is an easy way to kill an entire day.
But if the weather’s nice (and late September usually is) I would just spend the day walking around the 16th Street Mall.
I was there for an American Chemical Society meeting a couple decades ago and I visited the National Renewable Energy Laboratory in Golden, which is only a short drive from Denver, and I went to Mile High Comics. So you can see what a party animal I was back then.
The Denver Art Museum is definitely worth a visit; they have some good exhibitionswhile you’re here during GABF. DAM happens to be across the street and down the block from Pint’s Pub, where they make great beer, food, and have a tremendous collection of Scotch whisk(e)y.
The Colorado History Museum has some terrific permanent exhibits as well as some temporary ones that look pretty interesting. All of these places are within about a 7-minute walk from each other.
The Molly Brown House Museum is a bit of a walk from the area above, but it’s a great house museum celebrating the life and times of the “Unsinkable” Molly Brown.
I’ll second the Stranahan’s tour recommendation, and the 16th Street Mall really is great for people watching. Some beer-related recommendations for the mall:
[ul]Appaloosa Grill – has great food and is my favorite bar downtown; not a lot of draft options compared to bigger bars, but what they have is pretty outstanding[/ul][ul]Rock Bottom, which is a local brewpub chain[/ul]
[ul]Marlowe’s, which has great food and a big local beer list[/ul]
There are a ton of other options, but the three above (and Pint’s) are all locally owned. (ETA: an equity group owns Rock Bottom, I guess, but they still make good beer – the brewery, not the equity group)
Yep: as other posters note, Denver’s downtown isn’t big compared to other large cities, but we kind of like it that way.
Gordon covered a lot of the good downtown stuff but I’d like to add a couple.
The 16th street mall bus (free to ride) goes to the newly-refurbished Union Station which is an historic building in its own right and worth a look. They’ve added a lot of interest inside the station - restaurants, bars, shops, etc. - and it’s a nice place to spend a little time if you’d like to get out of the sometimes very hot Denver sun.
I’d also advise a short walk over to the football stadium, Sports Authority Field. Even when there are no games or events going on, the grounds around the stadium are interesting.
Probably not the type of entertainment you’re looking for, but there’s an amusement park, Elitch Gardens, right downtown on the C line light rail.
Finally, for a unique decor and dining experience, check out the Buckhorn Exchange which is also located at a stop on several of the light rail lines - 10th and Osage. The building is one of the oldest continuously-occupied structures in the downtown area and is a real piece of Colorado history.
[URL="http://http://www.buckhornexchange.com/history.php
You could go shopping for oxygen tanks while you’re ducking the space debris.
(I’ll just let myself out)
Listen to music…? 
…marches Burpo and the Count over to back-to-back kitchen chairs, ties them to said chairs and forces them to listen to John Denver caterwaul “Rocky Mountain Hiiiiiigh” for the next two hours.
Don’t Diss my Denver! 
HA! Mr. Deutschendorf is my hero and does no wrong (musically, anyway)!
Don’t Diss MY Denver! 
Great suggestions, everybody! The 16th Street Mall seems like a bigger version of Burlington, VT’s Church Street, definitely worth wandering around. I love Whiskey, so Stranahan’s is a must. I’m going to hit up Buckhorn Exchange for dinner sometime between Thursday and Sunday, but some of those other bars/restaurants look like good lunch stops.
Any other suggestions are welcome, I’m not putting my schedule together quite yet.