This mystery can be found in the southwest of Snotinghamscire, not far from the border with Sciropescire.
How to Complete Eorthburg Hlaw
When you arrive at the monument, be sure to read the inscription on the stone near the centre. To view the symbol from the correct angle, you’ll need to break the ice wall to the southwest. You can then enter the cave and turn around to view the symbol with enough distance to align it, thereby completing the mystery. Be sure to loot the other caves behind the ice walls before you leave.