Hit RiNo (River North) first. The street art alone is worth it. Union Station isn't just trains—it's where locals hang out, eat, and drink. Red Rocks Amphitheatre is mandatory, even without a concert. Try the morning yoga sessions up there. Check out the Santa Fe Art District on First Fridays, or grab tickets to a Rockies game at Coors Field. Those mountain views from the cheap seats are unreal. Rent bikes for the Cherry Creek Trail, or just drive an hour into the mountains. Rocky Mountain National Park is basically right there. Denver's grown into something real. Big enough to stay busy for days, but you won't spend half your trip just getting around.
Summer costs more and packs in tourists, but the weather's perfect and festivals run constantly. Fall through—September and October bring cool air, golden aspens, and way cheaper flights. Winter's for skiing. Spring is a gamble (snow in April happens). If your dates are flexible, shoulder season flights to Denver save you money and mean fewer people everywhere you go.
Denver International Airport is about 25 miles from downtown. That tent-looking roof is weird, but the airport itself is easy to navigate. The A Line train gets you downtown for a few bucks—way better than paying for a ride. For flight deals, fly midweek if you can. Budget carriers have been adding Denver routes, so finding cheap flights doesn't mean draining your bank account anymore.