The name is Finnish for something like a hill with a crest, and the Finnish coast has a lot of those: smooth, ice-scoured rocks rounded by the last glaciation and still rising from the sea by several millimetres a year.
The nearest mainland roads are straightforward and well kept, which is characteristic of Finland. The main road along the coast between Helsinki and the Russian border is fast and busy with trucks, and speed limits drop with the seasons, with winter limits lower than summer ones and cameras in the usual places. The small coast roads, by contrast, run through forest and over the inlets by little bridges, with farms, birch and spruce, and the smell of resin and tar. Moose and deer are a real risk at dawn and dusk, and a collision with a moose is no joke, so slow down when the trees come close to the road.
Summer is the time. Around midsummer it never really gets dark this far north, and the evening light turns long and golden. Mosquitoes can be fierce in July. In the shoulder seasons the Gulf can be grey and moody, and from December the sea freezes near the shore.
Kotka and Hamina are the places for fuel and a proper meal, and every village has a small shop that opens when it suits it. The fishing here is for Baltic herring and perch, and a good local dish is smoked fish with new potatoes and dill. Bring a map or a downloaded route, as the islands are not signed in the way a mainland town would be, and check ferry or boat access before going, because the outer isles are reached only by water.