Waymarks:  monuments, conspicuous route signs
Could this possibly be the Celtic Dolmen route?

High heaps:  very high pillars, megalithic stones.

Highway:  path, viaduct, high bridge or series of arches, to mound up, exalt, make plain.
The Celtic people have left their trail all over Europe and the British Isles with megalithic monuments, dolmen stone tables and stone altars.