Will you have a car? Where are you staying?
I'm not a city person so I try and get out of town as much as possible. Here's some mountain ideas but a disclaimer first so you aren't another tourist asshole fucking up my drive home.
If you are renting a car that isn't 4x4/ awd and want to head up to the mountains go to https://www.cotrip.org/home.htm
and check and see if there's passenger vehicle traction laws in effect. If there are and you don't have snow tires or AWD/ 4wd stay down the hill please. It's awesome when there's a rental car on crap tires spun out in the middle of the road making the drive even more fun. There's also really good traffic cameras giving you a pretty good idea what the weather is like.
Central City/ Black hawk is about an hour from Denver. It's one of the few places gambling is allowed. Blackhawk allowed modern buildings to be built but they have to "look old", central city still has everything in the original mine buildings. Central city is kinda cool to walk around. There's a couple cool old mines and a headfarme the old lady loves to take pictures of in Nevadaville just out side central city. I haven't found to go to restaurant up there yet. Drinks are still free if you are gambling.
Idaho Springs is technically a mountain town and cool once if you are a tourist. It was a major mining town and still has some things to see. Marions is great greasy soon breakfast, Tommy Knockers is a decent brew pub, smoking yards has good BBQ. I'm not sure if they do some of the mine tours during the winter or not. We did the Hidee last summer with some friends and they really enjoyed it but the Mollie Kathleen in Cripple creek is awesome (closed for the winter). If you are really jonesing for an underground mine tour and everything is closed hit me up, I can give tours of my work.
Oh my god road/ Virginia Canyon connects Idaho Springs to Blackhawk. It's a graded dirt road that's plowed though stay off it in a rental car if the weather is crappy. The views are great, there's a couple old mines to wander around/ take pictures of and a great way to loop Idaho springs to Central City/ Blackhawk.
The Peak to Peak Highway connects Estes Park to Central City/ Blackhawk. It's a nice drive. El-Mex Kal is awesome "real" Mexican food in Estes park. The Stanley Hotel is Estes Park was in the shining. Nederland is kinda an interesting hippy town. Driving back in rollinsville to the parking area for the moffet tunnel is neat, it's one of the few train tunnels through the continental divide.
We really like the national mining hall of fame in Leadville. We stopped for a "quick 45 minute trip" and were in there 2 hours and could have stayed longer if we weren't starving.
You could hit Idaho Springs for breakfast, ice races in Georgetown, mining hall of fame in Leadville. Giamapetros in Breckenridge has awesome Italian food but the wait can be long.
If you venture up I70 on a Saturday going up any time before 10am or down before 8pm sucks. Friday would be a good day to hit up the mountains if it isn't snowing, you would be coming home as most people are heading up I70