Of course the Horsetooth Reservoir makes a great sun-downer spot to enjoy the sun setting over the Rocky Mountains. On a clear day in spring you can even see white peaks in the background.
Location of the spot at Horsetooth Reservoir to observe the sunset. There’s a parking lot on the east side of the road from which you cross the road and can hike up the hill westwards to the circled spot. From here you have a great overlook over large parts of the reservoir and you can look into the marina bay.
Once you’re at the spot in the circle you can take pictures such as the ones shown below.
Blue hour at Horsetooth Reservoir (view in south direction).