I just came back from 3 days in Copenhagen. It is a really chill city, with friendly people and a very fast changing weather. We froze and sweated in the same day. Think of bringing an unbrella and a warm jacket if you go there!
The public transportation is straightforward and very efficient with trains and metros coming every few minutes. We barely ever waited. The city pass is very convenient.
We hit all the popular places, with our favorite activity being a ride on the goboat, plus we got to be there for the solar eclipse which made it extra special. We also loved the relaxed vibes of Reffen and highly recommend for you to stop there if you go to Copenhagen.
I would also advise you to go through the Kastellet fortress on your way to see the mermaid, where you can have a calm and pleasant walk and see the Kastelsmollen.
The people I travelled with also really loved Tivoli, but even though I had a good time, I think it could be skipped. It is, imo, overpriced and I much prefer wander in the city.
I loved my time at the Cisternerne museum who currently shows the 7 deaths exhibition, if you like opera and cinema I think you'd like it.
We found the city to be really expensive, the food in particular.
To sum up we all enjoyed our time there and I think it is a must see city in Europe!
Images locations:
Nyhavn
Amalienborg Palace
Ofelia Plads
The Little Mermaid
5-7. Norrebro
8-9. Reffen
11-12. Botanic Garden
13-14. Tivoli
Vesterbrogade
Kultorvet, Indre By
17-18. Christiania
19-20. Goboat ride