Short notice planning a trip!

So our original plan got scrapped so here’s our plan B- Pick a town out west( currently thinking of Denver or Seattle? Open to other suggestions)

Do 3-4 days in the city/ around exploring, going to cool places and sights

Then drive out to a cabin or state/ national park and relax and see the natural beauty- go on some hikes, maybe a hot spring?

Really looking for recommendations on cities, sites, maybe even air bnb/verbo ideas? Anything helps!