As Odysseus and his companions navigate toward the entrance to Hādēs, the atmosphere becomes ever darker. They are pushing the limits of the Extreme West, which the sun no longer illuminates. They are entering a zone where the sun can no longer be seen, O.11.015–016. Here the darkness that comes after sunset will be permanent, unlike the sunset that has already happened at O.11.012, which for the rest of the world will be followed by sunrise on the next day. But here, in this part of the world, the next day will never be found. Demarcating this zone, at the limits of the Extreme West, is the world-encircling cosmic river Ōkeanos, O.11.013.