Great exhibitions. They have a huge amount of artifacts and we spent a good 2 hrs walking through the museum. I recommend the Copenhagen Card, as admission is free.
The international section upstairs is amazing. The old display cases and just right lighting is something straight out of a Wes Anderson movie. You could spend hours looking through it all. ????
As for the collection, it is outstanding, so please go. The pre-historic part has just been brought up to date and is of internatinal standard. For kids, visit Børnemuseet at the ground floor.
Exhibitions are extraordinary and the museum covers various time periods from danish history. Besides you can find the ancient times there but be prepared for a long tour over museum.