Roskilde a Danish city with a fascinating history in its own right and whose origins date back to the pre-christian Viking age is most well known for the Danish Viking Ship Museum.
Jelling - Episode 18029
Today Jelling is a small town of less than 4000 people, however, it is considered to be the site of the the founding of modern Denmark.
Aggersborg - Episode 302
Viking Ring Castles in Denmark are a thing. First, that's awesome. Second, Aggersborg was massive and could have held 5000 soldiers!