A bus ride is organized on Sunday September 17th: it will leave Helsinki city center at 16.00 from Mannerheiminaukio bus stop next to the main entrance of contemporary art museum Kiasma in front of the statue of Mannerheim. (As a note: the same bus stop is used for IKEA bus).
Google street view: bus stop location
Participants are advised to arrive already on Saturday September 16th and to book one of the numerous hotels in the Helsinki city center. The Sokos Hotel Vaakuna Helsinki and Sokos Hotel Presidentti Helsinki are both a 1-2 min walk from the where the bus for the conference will leave. These are big hotels, rooms can be booked through https://www.sokoshotels.fi/
More information on Helsinki and accommodation can be found from http://www.visithelsinki.fi/en
Generally speaking, Helsinki city center is small and pretty much everything is within a walking distance.
For the travel back home, a bus ride will be organized in the morning of Saturday September 23rd at 9.00, taking participants to both the Helsinki-Vantaa international airport (if necessary, arriving at 10.00) and the Helsinki city center.
Information on public transportation in Helsinki region can be found in the journey planner (old or new version). We suggest to select the connections with the change at Leppävaara train station when going to/from the hotel. Please note that some of the connections require a 2 km walk to the bus stop from the workshop venue.