16.0 miles, Multiple days
If you are looking for the perfect hike in the Grand Canyon, this is it. The 2 (or 3) day hike will take you down into the canyon to where few visitors have the privilege of going. Although the Bright Angel trail is not as steep and has more shade cover and water, the views from the South Kaibab trail are unbeatable. It is best to start from the South Kaibab, hike down to the Bright Angel campground, and back up the Bright Angel trail. This way you get a change of scenery and can hike up where there is more available water.
If you have a few more days to spare, you can spend another night at the Bright Angel campground (there are some good day hikes from there), or spend a night at Indian Garden on the way back up to the Rim. However long you stay, it will be an experience to remember for a long time, as there is no better way to see the Grand Canyon that by staring up at it from the river below.
Bring LOTS of water, the air is very dry and you may not see visible sweat but you will be losing water very quickly.
It is hotter at the bottom of the canyon, make sure you stay in the shade and drink plenty of water (and go in the water to cool off).
Do NOT attempt to hike this whole trail in one day, it is too hot during the summer and there is not enough water.
Make sure you get an early start to avoid the hottest times of the day (and the early morning light makes the rocks walls look spectacular!)