You find the Thyphlo Ruins Skyview Tower north of the Lost Woods, but it's not working.
Tower Location
Thyphlo Ruins Skyview Tower is located at 0345, 3135, 0180. It is not within the Lost Woods, so you can go north from Goron City and then west along the road to reach it.
How to Fix the Tower
This tower isn't working, and Billson isn't sure why. You will see floating platforms around the tower. You can move these by attaching Zonai devices to them, such as the rockets that are on top of each one. Use Ascend to reach the top of the nearest platform, then attach a rocket to it so you can reach the other platforms. After you make your way to the top, you find a platform blocking the top of the tower. Attach a rocket to this platform and activate it to move the platform off of the top of the tower. Then go back down and talk to Billson.
Map the Region
After you fix the tower, examine the terminal to activate the teleport location here. Then step onto the glowing spot in the tower and examine it to be launched upward and map the region.