I never bothered getting the Ninja Gaiden games, since I suck at 2D games. To me they are infinitely harder than 3D games for some reason. I can't even reliably get through the first level of Super Mario World without dying. No joke.
Pfreak, here's what gamefaq's cheats and codes page says about the third game:
"Go to the peristyle passage in the Aquaducts, triangle jump back up to where you got the golden scarab on the top of the broken pillar."
In a walkthrough over there I found this section:
But if you already knew how to get to it, and just wanted to know why you couldn't pick it up, it mentions that you have to have Ninja Gaiden 2 already, but you said you already had that.
If you want, you can do both steps. After you've unlocked the door, there's
one more task you have to do. Go right near the entrance to this large pillar
room, but wedge yourself between two pillars around the right corner. It
should look something like this:
P - Pillar
R - Place Ryu here
| | - Put Ryu between the first two pillars sharply around
| | the right corner. Now, bird wall jump about 4 times
| | until you reach the top. You'll notice that the one
| | pillar has a section missing. You should land on top
| | of the broken pillar, and Golden Scarab #7 is there.
|P P PRP | This location is important as it is where you
|___| |_________| receive Ninja Gaiden 3 as well (check out the