What are some of the well known hiking trails in Colorado? Can you provide a short description of each?
Here are some of the well-known hiking trails in Colorado with a short description of each:

1. **Royal Arch Trail** - Boulder, CO: This trail is 4 miles long and has an elevation gain of 1,492 feet. It is rated as easy/medium difficulty and offers stunning views of Boulder's Flatirons and the city itself.

2. **Emerald Lake Trail** - Estes Park, CO: This trail is located in Rocky Mountain National Park and leads to a pristine mountain lake. It takes just under two hours to complete and isn't especially difficult but is easily one of the prettiest hikes in the state.

3. **Longs Peak via the Keyhole Trail** - Allenspark, CO: This trail is 14.5 miles long and has an elevation gain of 5,100 feet. It is rated as difficult and offers stunning views of Rocky Mountain National Park.

4. **Saint Mary's Glacier** - Idaho Springs, CO: This trail is 1.5 miles long and has an elevation gain of 700 feet. It is rated as easy and offers stunning views of a glacier-fed lake.

I hope this helps!
could you tell me the distance and the elevation changes of the Emerald Lake Trail？Which train would you suggest for running, i have experience running half marathons and would like to run a train that offers a challenge with some elevation, but is still runnable and has easier and harder sections interspersed. It should be under 10 miles.
The Emerald Lake Trail is a popular hiking trail located in Rocky Mountain National Park in Colorado, USA. The trail is approximately 3.6 miles (5.8 km) one-way and has an elevation gain of about 650 feet (198 meters), with a maximum elevation of 10,110 feet (3,081 meters) at Emerald Lake.

For a trail run under 10 miles that offers a challenge with elevation changes and a mix of easy and hard sections, I would recommend the Mount Sanitas Trail in Boulder, Colorado. This trail is approximately 3.3 miles (5.3 km) round trip with an elevation gain of about 1,343 feet (409 meters), with a maximum elevation of 6,863 feet (2,092 meters) at the summit. It offers a mix of steep and rocky sections interspersed with flatter sections, making it a challenging but runnable trail. However, please keep in mind that the trail can be crowded, especially on weekends.