This imposing structure is officially called Sandridge Lookout (or Webb Point Lookout depending what map you are using), but we prefer to call it the Singing Lookout. In a medium to strong wind the whole structure vibrates into the audio range, and can get quite loud. I wonder if the designers realized this.
The views from the observation deck are quite special though, and well worth the 800 meter walk out to the Lookout.
The cache is a 200ml sistema, and for a large metal structure, I guess saying it is magnetic is a bit superfluous.
Enjoy the walk (or ride)