Five days in Helsinki: looking for fun, quirky or unique things to do,

EDIT: Thank you all so much. We now have lots to choose from.
Questions:
- is there any need for local currency, or is everything tap-to-pay?
- are the buses and trams tap on/tap off or do we need to buy tickets or passes?
-is tipping expected at restaurants? and if so, what is normal?

We are a group of four older adults, visiting in August, and we are planning on doing a couple of the typical things: Porvoo, Suomenlinna, and some city walking to enjoy the beautiful architecture. We'd also like to get into nature for some trees and fresh air. [Is Turku worth a visit?]

We are hoping to find things that are special - we've found some information about the underground bunker system which looks really interesting and different from home. We are looking for more things like that; things specific to Helsinki or Finland. Think quirky little museums, fun cafes, authentic restaurants, city parks... We are not looking for party scene/clubbing.

I understand the vast majority of Finns will speak English, but we are concerned about things like signs, instructions and schedules for public transport, menus etc. Is that a valid worry? Also please let me know of anything that Finns might find offensive or irritating, so I don't make too big of a fool of myself.

On another note, which Finnish authors should I be reading?

Kiitos.

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u/TravelingChick — 2 days ago