One possible city in Finland with 5 letters is Oulu.
Oulu is a major city and the administrative center of the North Ostrobothnia region in western Finland. It is known for its high-tech industries and its beautiful location on the shores of the Gulf of Bothnia. The city has a population of over 140,000 people and is a popular tourist destination, especially during the winter months when visitors can enjoy a variety of winter sports activities.