Round, red-brick and 36m tall, the Gåsetårnet ('Goose Tower') gained its name when, in 1365, King Valdemar IV placed a golden goose on top of it. The goose was meant to mock a declaration of war made by leaders of the German Hanseatic League, who Valdemar had branded as mere ‘cackling geese’. The original model was later removed (and lost) by Valdemar's less heroic son, and the current version is an 1871 replacement perched on the tower's 19th-century bronze spire.
The tower was once part of a vast royal fortress. The rest, including seven other towers, was demolished over the centuries, but the Gåsetårnet was spared for use as a navigational landmark. If you want to go inside you'll need a ticket for the Danmarks Borgcenter (adult/child 125/75kr), which allows you to climb the tower as part of an extensive iPad-led virtual tour of the castle site's remains.