Copenhagen is always worth visiting, even if you have short time. I have visited 4 times and each time I felt very excited and amazed about its hundreds of historical and cultural attractions. The first one you should not miss is the Statute of the Little Mermaid because it is one of Copenhagen's most visited landmarks. It is located near the cruise ship pier of Langelinie. I love the fireworks shows in the Tivoli Gardens which happens twice a week and my children always asked me to take there during our visits. And some more interesting places you can visit are Rundetaarn, The National Museum and Amalienborg Palace Castle. If you find time, then just visit The Black Diamond, which is having a café, a restaurant and different kinds of exhibitions. Take a worthy visit and enjoy yourself.