Reader Tip: Chaos Rune Drop Spot, Powerlevelling Magic

Thecutezapp contributed a great little nugget of information I'd like to bring up to the front of the blog:

"Buy an air staff, lots of chaos runes and lots and lots of earths. Go to Varrock sewers and use the crumble undead spell on the skeletons, they drop chaos runes so you can stay ages. I got my mage up from 39 to 50 in one night!!!"

Great little tip for non-members, since Chaos runes are a difficult drop to find!

Where else can Chaos runes be found for non-members?