Starting at the beginning of September, the Northern Lights unveil their magical patterns on Iceland's starry skies. At the same time, Icelanders celebrate the "Retir": sheep and horses are herded to the lowlands. 4,500 sheep and 800 horses spend 3 to 4 months in the untamed highlands. Now, they are rounded up. No single farmer can herd so many animals to the lowlands. The entire community helps.