Sauna. Sormipaneelit (finger paneling?) on the walls look really good in black!
That's quite a cool idea, to have different coloured wood on the sauna walls. But then it would need decent lighting .
Nuoska integrated sauna heater by Tulikivi at Asuntomessut 2013.
Sauna ideas with stone wall. Nice use of indirect lighting, but I think we need windows too.