Haynach Lakes Trail is a 14.9 mile lightly trafficked out and back trail located near Estes Park, CO that features a lake and is rated as difficult. The trail offers a number of activity options and is accessible from March until October. Horses are also able to use this trail.
The Haynach Lakes Trail is amazing, so ignore the reviewer who gave it three stars. That reviewer is correct that it is not easy to get to, but with that said, you will not see masses of people there. When I was there, it was just a few people doing some fishing and one biologist studying fish populations. I did this trail as part of a five-day loop from Grand Lake, starting on the Tonahutu Creek Trail and passing over the Bighorn Flats to the North Inlet Trail. Unforgettable scenery! Haynach Lakes is a side-trip of that loop that is well worth the time. In addition to this, I would also recommend bushwhacking your way up to Bench Lake from the North Inlet. Tough hiking, but absolutely stunning.
Getting to these lakes definitely requires staying at one of the backcountry sites overnight. We stayed at Lower Granite Falls, and went to the lakes from there. The turnoff for this trail was tricky, because the sign only indicates the Haynach camp site, and not that the trail continues on the turnoff itself. The rest of the way to the lakes seemed farther than our maps indicated, and after a steep incline the trail more or less evened out into lush fields, which eventually led to the lakes. When we were there in August no one else was around, and there were still some snowfields around the first lake. While they were nice to see, I feel like there are more picturesque lakes in the park that take less effort to get to.