Gateway Towns & the National Forests -- Rocky Mountain National Park straddles the Continental Divide between Estes Park on the east and Grand Lake on the west. These two towns guard the entrances to the park, and we recommend making either of them your home base for a visit to the park. If you prefer, it is certainly possible to base yourself in Fort Collins, Loveland, or Boulder on the east, and Granby or Winter Park on the west. Denver is another possibility, and you can head to either side of the park from there; but staying there means you won't have much time to do any real exploring.
Don't forget that Rocky Mountain National Park isn't the only outdoor experience in this area. Nature's beauty does not suddenly stop at the park's boundaries, and there are plenty of things to see and do just outside the park -- and within an easy and scenic drive of an hour or two. The Arapaho and Roosevelt national forests adjacent to the park offer some of the best fishing and outdoor recreational opportunities in the area, and an outing to either of them will greatly enhance your vacation experience.