I went on a 3-day tour of Helsinki-Stockholm from St. Petersburg. Everything was great, we quickly crossed the border by bus, the first day we walked to Helsinki, in the evening we boarded the Silja Serenada ferry and went to Stockholm.
We went to Helsinki for 4 days, stayed with a relative. There are not so many attractions in the very center - the church in the rock (the outfit does not look good), the monument to Alexander II, Jean Sibelius, Manerheim, a very beautiful Lutheran Cathedral on Senate Square, the parliament building...