Each year in the heart of southern Sweden, a special lake hosts a natural spectacle. It's a stop-off point for more than 10,000 cranes migrating northwards. The sight of these huge birds milling around on the icy banks of the lake is a remarkable sight in itself, but the best is yet to come. As the spring sunshine melts the snow and ice, the cranes start to dance. Once seen, the dance of the cranes is never forgotten.