There are a lot of great places in Helsinki. I and my wife have a hobby of playing tourists in our own city. For example last summer, we visited Hernesaari, which is an interesting area and worth visiting. A memorable and special place was also Sompasauna in Sompasaari.
I think that the real Helsinki can only be found in Kallio and Sörnäinen areas. The atmosphere and environment differ greatly from those in the city center, on the other side of the Pitkäsilta bridge.
In Kallio, there is a huge variety of exceptional and interesting pubs and bars. When I was younger, I used to go barhopping there once a week. I started in the morning and kept going until it was nighttime. In these places they have morning and night shifts, meaning that other people show up in the morning time and other in the evening.