Alright, so I saw the artifacts up there yesterday and decided to poke around to see if I could find a way up.
My solution was to run up the arch, obviously and before you get to the slope that knocks you off, turn around and jump onto the railing. I could only make this solution work from the north-easterly arch (closest to Sanctum on the north side) and I'm not sure if it's really easier there, or if I'm just better at jumping that direction. There was only one artifact up on the other side of the arch and I was a bit frustrated seeing as I had tried to get up over there for quite a while with no luck, but before I consigned myself to jump off and try on the other side I thought I should at least see what I could do up there.
So I jumped at the pillar, the furthest spot up I could get and just kept jumping (think trying to get up a slope, slightly different angles and such). I found little ledges, easily, and just started going along them. Low and behold you can basically push yourself against and slightly underneath the big arch and get to the other side. I had no issues going back and forth and looted my artifact.
Now hopefully I can do it again the next time.
EDIT: It's actually just an invisible bridge from one pillar to the other, not sure if it's intentional but no jumping is required once you get onto it. Yay.
Edited, Mar 1st 2011 1:33pm by Shujiko
<Conqueror of Mountains>