Rocky Mountain National Park – Colorado Popular hikes in Rocky Mountain National Park: 1. Mills Lake - It offers spectacular views both on the trail and at the destination. 2. The Loch - A hike of 6 miles round trip brings hikers to this beautiful subalpine lake. If you’re up for a longer hike, you can continue to the Lake of the Glass and Sky Pond. 3. Flattop Mountain - The summit sits at a little over 12,000 feet and offers 360 degree views of the greatest peaks in the park.