stuck in chapter 3 or 4?

[steelth1]

found a video on you're website i think. i was wasting my guardian trying to kill everything instead of going right to the boss. you need full health in the guardian to beat him. also i was shooting the ball on top instead of the bunker. much faster that way. sill could use your help though. now I'm stuck where you need the blue crystal to wake up the guardian. i can see it up high on a wall ( that's where my compass points to) but i don't know how to get it. i know it must be simple because nobody else asks about it but i don;t see any lever or any way to get to it. thanks again