How the hell do I get the Relic which is east of the "Amanaki outpost"?

Such a new game there are limited guides out there, other than links to sites where the claim to have a guide, you get there and it says "coming soon" Annoying huh?

Anyway this relic is driving me bonkers I've been round the hill so many times. Tried all 3 of the black dots which are caves. The two you can see are connected, the third is under my cursor, nothing in there but skulls.

Here's a pic:-

http://imgur.com/TUFx1

Anyone any ideas?