Réttir is an annual event which typically takes place in September, as the season turns from summer to winter. During réttir, horses and sheep are rounded up from the mountains where they've spent their summer months. Horses which have stayed on the farmland during the summer months also play a pivotal role in réttir, helping the farmers to round up their flock. The farmers drive the animals down from the mountains and into pens, where they separate their flock from the rest of the sheep.