This page explains how to reach and climb Tabantha Tower, in the west of Hyrule.
How to Reach Tabantha Tower
From Shae Loya Shrine, go across Tabantha Great Bridge (to the west of the stable). You will see a Guardian Skywatcher on the path ahead. To avoid it, if you are on horseback you can carefully avoid their spotlights, or if you are not on horseback you can climb up the hill just after the bridge. Go northwest on the hill.
From there, go to the hill with the tower on it. You can make your way up the hill, battling Bokoblins, Lizalfos, and Moblins, or you can just stealthily climb up the hill in places where enemies are not patrolling.
How to Climb the Tower
At the tower, climb the column southwest of the tower, then shoot an arrow down at the eyeball on the column north of the tower. This will make the column fall onto the tower. Go up the fallen column and climb to the top of the tower from there.