I recommend starting this hike from Bear Lake. The trail up the moraine from the Bierstadt Lake Trailhead is steep, dusty and hot in the summer with little tree cover. However, if you start from Bear Lake you are hiking in the trees and after climbing up the moraine for about 1/2 mile the rest of the hike is downhill to the lake. The trail from Bear Lake is about 2 miles long with an elevation gain of about 200 feet and an elevation loss of about 234 feet. The return trip can either be back to Bear Lake the way you came or you can hike down the moraine to the Bierstadt Lake Trailhead and take the shuttle bus back to Bear Lake if that is where you parked your car.
As you approach Bierstadt Lake on the Bear Lake Trail, the trail splits left and right. The left trail takes you to the junction with the trail to Hallowell Park and the trail around the lake. The right trail takes you down the moraine to the Bierstadt Lake Trailhead. Take the trail to the left and unless you want to go to Hallowell Park, stay on the trail around the lake and when you see the horse hitch area leave the trail and head South (right) to the lake. I personally like to sit on the sand beach at the end of the lake and take in the view of Flattop Mountain and Hallett Peak.
This hike starts at the Cub Lake Trailhead, which is on the road to the Moraine Park Campground. There is also a shuttle bus stop at this trailhead. The trail is fairly flat at the beginning as you work your way into Moraine Park. As you get close to the lake, the trail begins to climb up to the lake. The trail to Cub Lake is about 2.4 miles long with an elevation gain of 540 feet. The return trip is either back the way you came or you can hike up to the Fern Lake Trail and follow it back to the Fern Lake Trailhead. From there you will have to hike another mile to get back to the Cub Lake Trailhead. The last time I hiked this trail, we saw several moose right next to the trail.
Tyndall Gorge Lakes
Bear Lake, Nymph Lake, Dream Lake and Emerald Lake. Normally these lakes are hiked in sequence and is the most popular trail in Rocky Mountain National Park. Nymph Lake is 6/10 of a mile up the trail from Bear Lake with an elevation gain of 250 feet. Dream Lake is ½ mile up the trail from Nymph Lake with an elevation gain of another 200 feet. The trail splits at Dream Lake with the trail going South (straight) to Lake Haiyaha and going West (right) to Dream Lake. Emerald Lake is 7/10 of a mile farther up the trail from Dream Lake with an elevation gain of another 200 feet. The total length of the hikes to these lakes is about 1.8 miles long with a total elevation gain of 650 feet. The return trip is the same way you came up.
This trail starts at the Bear Lake Trailhead and you hike past Nymph Lake to Dream Lake where the trail splits. Go South (straight) to hike to Lake Haiyaha in Chaos Canyon. Lake Haiyaha is Indian for Lake of Many Rocks, which you will agree with if you hike there. The trail to Lake Haiyaha is about 2.1 miles long with an elevation gain of 770 feet. The return trip can be done two different ways. One is to return the same way you came up. The second is to descend down to the Mills Lake Trail. I cover this route in my long hikes section.
This trail starts at the Gem Lake Trailhead on the Devils Gulch Road. The trail to Gem Lake is about 2 miles long with an elevation gain of 1,080 feet. Parts of this trail are very steep. This lake is in the Lumpy Ridge area and this is usually a hot and dry hike in the summer.