As a Dane, I quite often forgot how awesome my own country is and sometimes I need to be a tourist in my own country and really see what everyone's fussing about. Copenhagen is the number one spot if you want to fall in love with Denmark. It got beautiful architecture and delicious food! I recommend a weekend trip to Copenhagen, however, if you only have one day it's all good. Here's some tips on what you can do in only one day!
Nyhavn was once a busy comercial port for ships from all over the world. Now it's dominated by restaurants with authentic Danish foods and the iconic colourful houses, which are an important part of Copenhagen's identity. It's the perfect place for lunch, a cold one or an ice cream - the options are many here. Nyhavn is also where the famous Canal Tour starts.
If you want to experience on of the best views of Copenhagen, do it from the tallest tower of Copenhagen. The Tower is located inside Christiansborg Palace (Prins Jørgens Gård 1) and it's completely free to visit! It's open between 11am and 9pm all days except Monday, however, be ready to stand in line for a while; they only have room for 40 people at the same time. To beat the crowd, try coming as early as possible or later in the day.
When you are near Christianborg Palace anyways then head by the famous little street, Magstræde. The street is one of the few old preserved streets from the 1600 or 1700 with cobbled roads and old colourful brick houses.
Rosenborg Castle is located inside the King's Garden, which is also worth a visit. The garden is full of beautiful flowers and alleés (avenues). Rosenborg Castle is one of the most beautiful castles in Denmark (in my opinion) and is located right in the middle of Copenhagen. It was built for King Christian IV. The garden is free to visit and so is the castle - on the outside at least. The museum costs 115 DKK and this is where you'll find the Danish Crowns and the Danish Crown Jewels.
The church, located right next to the Queen's home, Amalienborg, is a magnificent marble church (hence the nickname). It resembles the churches of the Vatican City with the beautiful dome in the middle. The church is located on Frederiksgade 4 and is free to visit every day between noon and 5pm. Afterwards it would be pretty stupid not to go the 100 meters down the street to see Amalienborg Castle.
Other must sees in Copenhagen if there's time: