The standing stones at Tionontate:ken are found at the center of Vinland, just northwest of Teiotenontatase:ke synchronization point.
How to Align the Symbol on the Tionontate:ken Standing Stones
To see the symbol on the stones you’ll first need to use Odin’s Sight to make the symbol appear. The symbol of the rocks can be seen from the top of one of the standing stones, however, before the symbol can be seen completed you’ll need to move two movable rocks out of the way.
Once you’ve headed up onto the rock you’ll have to adjust your camera until the symbol has aligned and you complete the mystery.