The reservoir is beautiful! There is a easy foot path to stroll surrounding the water. Other hikes recommended here: Palisade Falls - easy Grotto Falls - easy Hyalite Peak trailhead - many waterfalls to see along the way
There are two entrances to the national park, each about 1.5 hours away. The North entrance in Gardiner, MT and West Yellowstone.
Easy out-and-back hike.
Intermediate out-and-back.
More advance hiking due to incline. Out-and-back.