Cathedral is design by Carl Ludvig Engel, German born architecht who have made most of the square's buildings.
Entrance is free.
This is not very decorated cathedral.
There are quite often concerts that are fee entrance, sometimes you must pay a ticket, or there is small (5-10 euros) program free.
In Sunday mornings at 10:00 (am) there is regular service (as some other times too). In that time it is not open for turist.
If you own or manage Lutheran Cathedral (Tuomiokirkko), register now for free tools to enhance your listing, attract new reviews, and respond to reviewers.