What is gluhwein and how is it traditionally prepared?

Gluhwein is a traditional German hot mulled wine typically enjoyed during the winter holidays. It is made by heating red wine with spices like cinnamon, cloves, and citrus fruits. Sugar or honey is often added for sweetness. The mixture is simmered but not boiled to preserve the alcohol content. It is served hot and garnished with orange slices or cinnamon sticks.