If you enjoy hiking in the Eastern Sierra, then you have to hike Duck Pass Trail. It is one of the most popular hikes in the Mammoth Lakes area, but you can avoid the crowds if you hit the trail mid-week or after peak summer season (in September or October). It is a little over 7 miles (round trip) with about 1600 feet of elevation gain. One of the great things about this trail is that you don't have complete the whole thing to have an amazing experience. You can stop at Arrowhead, Skelton, or Barney Lake if you want to shorten the hike and you will still have an amazing outdoor adventure.
To get to the trailhead, drive all the way up Lake Mary Dr. and turn left at Lake Mary. As you drive around Lake Mary you will see Coldwater Campground on your left, turn into the campground. Drive all the way to the end of the campground and there will be a large parking lot. There are several trail heads for different hikes in this area, so make sure you are at the right one. As you start the hike it pretty quickly starts going uphill. There area a couple miles of incline right at the beginning of the hike, but it mellows out until you get to Barney Lake (for the most part) once you pass Arrowhead Lake.
There is a side trail down to Arrowhead lake just few miles. If you are just looking for a quick hike, that is great stopping point, but I highly recommend continuing on to Skelton Lake. The photo above shows Skelton Lake and you can see Duck Pass in the distance. Skelton is a great lake to take a break and maybe eat a snack before you continue on your trek. You will hit a few more areas of uphill hiking, but it isn't to difficult for the next couple of miles.
Even through this is a well traveled trail, it doesn't take long before you feel like you are out in the middle of nowhere. The wilderness out here is particularly beautiful and there are a ton of places to stop and take photos or just relax on the way.
Barney Lake is actually a couple small to mid sized lakes at the base of Duck Pass. It is a great stopping point for anyone who doesn't want to do the whole hike. There are a couple of off-shoot trails that take you around the lake to areas where you can be totally alone even on a busy weekend. I didn't do the whole hike to Duck Lake on this day, but if you want to continue, this is where it gets difficult. There is an exposed ridge with a whole lot of switchbacks that takes you up to Duck Lake. As you go through Duck Pass at the top of the ridge, you will see Duck Lake in front of you. You aren't officially done with your hike until you walk all the way down to the spillover section towards the bottom of Duck Lake. It is a commitment, because you have to walk all the way back up that incline on the way back; but as locals will tell you, you have to make it all the way to the spillway to officially complete the hike.