Casting another far sight while channeling a far sight will let you "jump" your vision further and further ahead. With practice, you can view anywhere on your continent with this technique.
To do this, simply use Far sight. Then, while under the spell, click your Far Sight spell, and move the camera further. You can move around corners, and far ahead of your normal line of sight.
Spying! Going to take a risky venture into the enemy city to speak to the Elder there or attack their Bonfire? Use the technique above to scout out a safe route!
Explore! Curious about what lies beyond that impassable mountain ridge? Use Far Sight to take a look.