My parents bought a home in Estes Park outside of Rocky Mountain N.P. Colo. in 1976 and we lived near there for another 7 years before eventually coming back to Texas. We sold the place after they both had died, but my older brother and a sister bought homes there, so I have been walking those trails almost every year for over 40 years. There are two walks that are my favorites. One I take flatlanders on is to park at Bear Lake @ 9,450 feet and trek mostly downhill, after about a 2/3 mi. upward trail, down to Bierstadt Lake very early in the morning before the wind gets up. On the far side of that lake you can often catch a perfect reflection of the up close Rockies including Long's Peak. Absolutely stunning panorama of the whole range from there. Then it's an easy walk from there down to the main road to a shuttle bus pickup point where you can ride free back up to Bear Lake to get your car. Easy walk for the tourists with great views, especially in the fall when the aspen are turning and the elk are in rut. Bugling can be heard for miles during that time.
The harder walk has to be in August and early Sept. depending upon how long it takes for the snowmelt to open the trail. The Glacier Falls Trail near Bear Lake goes past those falls, up past Mills Lake and on to Black Lake where you can look strait up a stone facing about as high as Stone Mountain Ga. and watch the snowmelt tumble down off that facing strait into the lake. It's a daylong round trip so take plenty of water, energy bars plus raingear because often you get thunderstorms that are coming over the Rockies there from about noon on that time of year.
If you are on a hike with me in the Park and I tell you we need to turn and run back downhill to the car, then you just have to trust I know how to read those clouds after so many years learning the hard way what they mean when they first start to build before tumbling over the mountains with a lot of lightning and heavy rain. A friend I took had a hard time believing me and kept slowing us down to watch. So the last 400 yds we sprinted with lightning, small hail and rain. Sometimes you just have to trust someone else's experience.