Viewpoints can generally be found high up and give a great view of the area.
Viewpoints are marked on your map with an Eagle
When you arrive at the viewpoint (usually requires a lot of climbing) you can then synchronize with the area. This will reveal the map around the viewpoint and will highlight collectibles and other points of interest.
You can also fast travel to view points once the fast travel feature gets unlocked.
You can generally quickly get down from a viewpoint by just moving forward and jumping down - what's known as a Leap of Faith
