Rocks are the only abundant 'resource' on the Aran Islands; Inis Mor, the largest of the three, is about 10 miles long by 2 miles wide, but the tour guide said that there are approximately 7000 miles of stone walls on the island. They made walls partially to keep the soil (only a foot deep on most parts of the island, and largely made from composted seaweed dragged up from the surf) from blowing away, and partially to have a place to put all of the rocks. My grandfather would have loved this place.