The beautiful castle Olavinlinna is the landmark of the city. For those who appreciate useless trivia: the first water closet in Finland is in Olavinlinna, those bumps on the towers. Structure-wise they are closets, there's a seat with a hole (a seat made of rock, I've heard in winter time there was a slave warming up the seat sitting there butt naked), and if you look into the hole, you can see water, the lake, where all the products eventually dripped and dropped.
And from toilet to table: there are certain food that you just have to try if you visit. Please find the top tips below, in priority order:
1. Lörtsy - a flat pastry cooked in oil. It can be savory (filled with meat and rice) or sweet (filled with apple, sugar on top). The one and only place to eat Lörtsy is at the market place, in one of the coffee booths.
2. Muikku - vendace that are rolled in rye flours and fried in butter. If you quickly have a portion of muikku at the market place, you can eat them with your fingers. But if you have something on the side, then you'll need fork and knife. Restaurant Seurahuone right next to market place, at top floor, is the place to go for Muikku. And by the way, when taking a photo, we don't say "cheese", we say "muikku".
3. The sandwich of the house at restaurant Majakka. Heavy stuff, doesn't leave you hungry.
4. Ice cream at Lippakioski. Huge ice creams, at half of the price you pay here in Helsinki. You can find Lippakioski if you start walking along the shore from market place to Olavinlinna castle.
5. Rommipulla - rum bun. A cinnamon roll filled with rum-flavored cream. Perfect combo. You can buy these at the market place. I don't now remember which of the market stalls it is, but keep your eyes open.
The only challenge with all this delicious stuff is time: you can't eat all of them during one day - so staying over night is a must.