Warning! The SOL cache series expose the geocacher to excessive UV radiation in an environment where it feels comfortably cool. Do not get a sunburnt, since it raises the risk of skin cancer significantly. There's nowadays also mites in the Helsinki archipelago that are contaminated with the TBE virus. The proper means to hedge against the disease (Kumlingen tauti in finnish) is the vaccination.
The round trip ferriage to Pihjalasaari is 5 euros (originally 4.5 euros back in 2004). You can also use your own boat, or camp in a tent overnight (cf. the link) but it's not allowed to bring a bike in here. While you're on the island, be sure to also check the Krepost Sveaborg I (GC78F9).
Go to the coordinates listed above. Enjoy the 180° breath taking view on the Baltic Sea. Relax. Then slowly turn to your left so that you're looking towards the northeast. There are two manmade objects. One with colourful stripes and the other one right next to it. Count the stripes and let that number be x. What's that thing in the tower up there? (Finnish is cool too.) Count the letters of that word and let the number be y. Furthermore zzz = 18.8 * x * y and nnn = 819 + x + y. The last stop is located at:
If you need assistance on finding the right Merisatama harbor platform to Pihlajasaari, you might want to add the coordinates N 60°09.204' E024°56.478' to your GPSr. Trams 3B and 3T going to Eira are probably the easiest public transport method available.