Copenhagen airport layover

Take the train to the central station (a few minutes) or the metro to Kongens Nytorv and walk around. This is likely the easiest airport in the world to sneak away for a few hours and see quality things.

Agreed, it takes about 15 minutes to reach the city by either train and metro, so that’s what I would do. What to do in the city depends on your interests, and Visit Copenhagen can maybe offer some inspiration for a few hours. If you want to just stroll around, and maybe finding a café somewhere, I’d recommend going to Kongens Nytorv and start there. If you’re a little tired from the flight, maybe a canal tour could be nice. They leave from Nyhavn and take about an hour.

Copenhagen is one of the most fun capitals in all of Europe so—by all means— take the train from the airport into the city and have a look around. Even with just a few hours, you’ll be able to see some of København and—most especially— get to mingle with some of the friendliest people in Europe.

Have a great trip!

Adding on to the OP question:

We're flying from US to Berlin with a 4.5 hour stop in Copenhagen.

Is the above advice still valid after doing whatever passport/customs control are needed?

Thanks!

We're flying from US to Berlin with a 4.5 hour stop in Copenhagen.

Is the above advice still valid after doing whatever passport/customs
control are needed?

To this question and the OP, assuming your flight from US is on time, you'd need to: get through immigration and EES (if it's up and running); if you have bags, find a place to stash them; find and use transport to city; then return to airport at least 2 hours ahead of your flight to get back through security. That will cut your sightseeing time way down. I myself would pay for an airline lounge pass and stay at the airport, but I am risk averse.