Quiz a local on what the most well-known structures in town are and they'll probably mention Cloostaarnet. It's one of the first things you'll spot when you begin sightseeing.
When you've finished up at this Frederikshavn modern piece of architecture, why not check out Bangsbo Estate, Kattegat Silo, and Frederikshavn Harbour? They're not too far from Cloostaarnet and also popular with tourists.