For a work training. I'll have half of one day on my own (with daylight) and want to see as much nature/cool stuff as possible. I'd kind of like to see the Red Rocks amphitheater (cuz I like U2

) but any advice from anyone who lives near there/been there? I've never been there. It will be in February.
I won't have a car, but was thinking about renting one that day (the day I get in) to hit the road running.
I will have late afternoons/evenings to explore the city as well.
Any suggestions?