Copenhagen has several outdoor rinks that pop up in winter, mostly from late November through February, depending on the weather. Expect a casual, friendly scene rather than a polished tourist trap. The ice is usually decent but can get crowded on weekends and evenings, especially near the main squares. It's a nice way to spend an hour if you already like skating or want to try it; the setting with city lights and people-watching makes it pleasant even if you're not an expert. If you're visiting in summer or early autumn, skip it entirely—there are no year-round indoor options geared toward casual visitors.
Expect to pay around 80-150 DKK for skate rental and entry combined, sometimes less if you bring your own skates. Weekday afternoons tend to be the best time: fewer people, calmer ice. One honest tip—pick a smaller neighborhood rink if you want to actually skate rather than shuffle in a crowd; the big central ones are more about the atmosphere and hot chocolate than serious gliding. Skip renting skates if your feet are larger than a EU 45 or so; selection gets thin and the rentals are often well-used.