Topic: A little question on Phantasy Star...

How do you open secret doors in dungeons?
http://www.psalgo.com/phantasy-star/maps/casba-f1.html
As you can see here, the bumpy green parts indicate a secret door. The problem is I can't even see them, never mind open them. Help?

If I remember right you can walk through some walls, maybe that's what they are.

I tried that. Do I need Noah's spell to unlock magically locked doors?

But I still can't even see them, do I need something else or a different spell?