I have a feeling that for Finland's very short summer season Mariehamn might be considered a resort, but the term has negative connotations for me and it certainly is a popular sight. It has masses of tourists every year but it remains a beautiful town, a very worthy island capital, even if it were not THE ONLY town on the islands.
Many people have only seen its western harbour on the course of a voyage between Finland and Sweden. This is an alluring sight, with the Viking, Silja and Tallink terminals and the museum ship Pommern.
In fact, the island is very narrow at this point and it is only a quarter of an hour at most to the eastern shore with its marina and lovely parkland, to say nothing of the island assembly building.
There is a limited amount of urban transport, which is free and five bus routes to different points on the main island. Sadly, but understandably, these are NOT free!
There is a considerable choice in restaurants and accommodation, but they don't spoil the nature of this island capital -- they enhance it. Whereas there is building (they don't want their rising population to be driven out by lack of homes), they are not making the mistake that has been so common elsewhere in Europe of destroying what was of appeal to their early visitors. Here the whole coast remains attractive. Long may it continue.