For a short city trip, you do not think so quickly, but Helsinki is definitely a must for a weekend away. The climate is colder than here and the greatest chance of good weather is in the months of May to August. The city is only two hours flight from Schiphol Amsterdam, so the travel time for your city trip is very good. When you arrive at the airport, you can from there take the train directly to the centre of Helsinki. Also very easy. The city is a bit strict at the beginning with many tight, robust buildings. But if you walk around for a while, you will see that most buildings are simply beautiful, and the architecture is very beautiful.
Like nowadays in many foreign cities, you can also rent a bicycle in Helsinki for a few euros. 140 bikes are ready at 140 points. Registration is very easy via the site Kaupunkipyorat. If you also download the app you can see exactly where the bikes are and how many are still available at that location. The bikes are firm and cycle well.
Worth visiting are the museum Ateneum, the Design Museum, the market halls, where many nice coffee shops are located, and in the centre of the new swimming pool. From the large terraces (free access) you have a magnificent view of the water and the city.
I think it is best to book an apartment so that you can cook for yourself. What I like the most, is in the afternoon somewhere to have lunch and cook in the evening. A supermarket with a huge range at good prices is in the basement of the Stockmann department store in the centre of the city. Here you will find products from Finland, but also from the rest of the world. The prices of wine and other alcoholic drinks are significantly higher than in the Netherlands, but otherwise, I did not find it much different from our price level. Helsinki is therefore very good to do for a weekend away. The clean air you breathe is literally a breath of fresh air. It made me feel like I came back a bit healthier than I went.