This is a very scenic, moderately difficult hike up the gentle slopes of Green Mountain outside of Boulder. The highlight is a natural rock arch spanning about 20 feet of air, which the trail passes right beneath. The view from here is great as well, stretching all the way to Denver's skyline and across the Great Plains.
Multiple routes in the mountain park link up with the Royal Arch Trail, but the most direct access via Bluebell Road, from either Chautauqua main parking or Enchanted Mesa parking. Walk up to Bluebell Shelter and begin the trail from there.
The hike begins as a gradual incline through shady Bluebell Canyon. Soon you will start to switchback up a piney ridge and gain a vantage of Boulder and the surrounding landscape, including the Flatirons. You will drop down again for a short distance, then back up, starting a somewhat steep, final climb. Soon after the start of this steep section you will pass Tangen Spring, which trickles with water most of the year. There is a small cave here that kids (or adults) can crawl into and explore. For the more intrepid spelunkers, climbing up and out the back of the cave affords a great view of the arch that not many people get to see.
Royal Arch is an eroded outcrop of the Fountain Formation, the hardened sandstone layer that is exposed all along this part of the Rocky Mountain front. It is the same type of rock that makes the nearby Flatirons. Once you reach this spot, take time to relax in the shade, rehydrate, take in the views, and enjoy your reward for finishing the hike.
Note: This is a Voice and Sight Trail, which means that dogs are permitted off leash with the following conditions: (1) Guardians must be registered in the Voice and Sight Tag Program, (2) Voice and Sight Tags must be displayed on the dogs, (3) Guardian has a leash for each dog, with no more than two dogs.