This page explains how to find and climb Eldin Tower, in the northern area of Hyrule.
How to Find Eldin Tower
First, you should find and activate Lanayru Tower. Then from Lanayru Tower or the nearby Soh Kofi Shrine, go north to a path that goes northeast. Follow this path, going left at the fork (the left side of the sign says Maw of Death Mountain). Soon after you go left, you will see a shrine in the distance. Keep following the path and you will reach Foothill Stable. Go east from the stable to reach Mo'a Keet Shrine.
From there, go north on the path from the stable. You should be able to see the tower straight ahead. As you go north on the path, you reach the Maw of Death Mountain area, where there is a hot spring surrounding a rock path. If you get in the spring, your hearts will slowly be restored.
After going past the hot spring, there will be a Guardian Stalker on the right. You can go left from here to climb up the volcano wall and reach the tower quickly.
How to Climb Eldin Tower
Climb to the hill near the base of the tower, and jump from there to the tower, where you can climb up the platforms to reach the top.