City name is a city in Region name.
You can daily come to Sønderborg with plane from Copenhagen. About 150 km from Sønderborg, is Billund Airport located.
From the most of the danish cities you can com with train to Sønderborg. DSB
Sønderborg is located not very far from the Danish-German border. Just south of the border is the German town of Flensburg which is popular amongst Danes going to Germany on a one-day trip, often to shop & to buy alcohol and chocolate which is cheaper in Germany than in Denmark. Except for cigarettes, they are slightly cheaper in Denmark rather than Germany nowadays.