This is an 11 mile round trip hike with an elevation gain of 1,900 ft. My guide book says it should take about 5 hours to complete and is rated easy to moderate.
"The Hyalite Creek Trail is the premier hike in the entire Bozeman area. The trail passes eleven waterfalls in a deep canyon with massive cliff walls and majestic peaks. The hike ends at Hyalite Lake, a high mountain alpine lake in a horseshoe-shaped basin."
For more info: http://www.rei.com/guidepost/detail/montana/hiking/hyalite-lake/40431