An enjoyable road, 1543/11775 Emäsalontie, leads from Tolkkinen (SW of Porvoo) to the tip of Varlaxudden in Emäsalo. You'll want to park before the gate and the guys with loaded assault rifles, though, and take a short walk along the barbed wire fence (watch out for stray wires) to the SE tip of the peninsula. There's quite a view. But be careful where you point your camera...
The cache has to withstand the harsh environment and loads of evil geomuggles, so please be stealthy, close the lid well and hide the box thoroughly.
PS. do visit Four Elements: Wind (GCGW8C) and VOR/DME PVO (GCQTEE) on the way, if you already haven't...