Sable

These look like a temple or round base with a big piece floating above it. They will have rings in the sand near by. To get them to rise you have to light up the rings by driving your bike through them. In both cases there were 4 rings to pass through.

I've found two so far, one is right next to the Dunboyne in the second area, east of Burnt Oak Station.

The next one is south of Eccria.