The Pitkin Creek trail starts in East Vail and gains 2900 feet in elevation over 4.5 miles and ends up an alpine lake at 11,4000'. The trail is a bit steep at the beginning and then it changes to a gradual climb. About 2.5 miles into the hike, you encounter several switchbacks, thinking you are close to the lake. What you come upon is a series of false summits, until finally getting to a beautiful alpine lake. Allow about 3 hours up and 3 hours down for the hike, as well as time to hang out at the lake. Here's a link to a very good trail map from the US Forest Service: http://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5186388.pdf
You may see llamas on the trail.
Great views on the hike up.
The alpine lake at 11,400'.