This is an absolutely gorgeous trail run along the Upper Big Water Trail/Great Western Trail to Dog Lake. The leaves are incredible in the fall. I highly recommend this trail while the leaves are changing colors. The trail itself is very nontechnical, allowing you to take in the views around you rather than maneuvering a rocky trail.
Drive all the way to the top of Millcreek Canyon until you can't drive any further. (They close the road further down the canyon in the winter so this trail is not accessible to cars in the winter.) There is a small parking lot at the end of the road, park here. The trail head is going to be on the south side of the parking lot. Mountain bikers frequent this trail, but are not allowed on odd-numbered-days.
This particular route is about 6.2 miles round trip, but there are quite a few different trails that connect to various parts of the trail, so you can make it as long as you want. There are a few signs along the way that will help guide you to Dog Lake. The elevation at the lake is 8,743 ft.
Dogs are allowed on the Millcreek side, but you can't take them past Dog Lake into the Big Cottonwood side because of watershed laws. Take a few minutes at Dog Lake and snap some awesome photos and pause and take in the beauty of the nature around you.