The Oiolad was a sparsely populated plain about 100 miles wide between Arthedain and Rhudaur. Low grasses covered the gently rolling landscape. Angmarean patrols were common here, and even the Hillmen stayed away when they had the opportunity.It encompassed both Dyr Erib, the "Lone-lands" on Rhudaur's frontier, and Dyr Úvadan, the "No Man's Land" on Angmar's frontier.These chalk-prairies stretched a hundred miles north, east, and south of Weathertop. Its southeastern portion was flat and featureless enough that crossing the plain could be as dangerous as traveling the deserts of Harad. The soil here was thin and rocky, the grasses short and tough; the land was drier because much of the rain drained away underground through cracks and passages in the limestone bedrock. The rivers and streams that did exist cut ravines and narrow valleys, with stands of small poplars and willows growing near the water. The Menatar Romen, the Great East Road, crossed the Dyr Erib between Weathertop and the Last Bridge over the Mitheithel. The old Arnorian engineers had provided culverts over the ravines and cisterns every five miles where there were no streams. The Hagavorl, the Cardolandren border hedge, had a defensive road running southeast from Weathertop that also had cisterns. These two routes provided the best means of crossing the lower Dyr Erib.
- MERP:Northwestern Middle-Earth Gazetteer