Majamaja will eventually be a cluster of five cabins, one of which has already been completed, and a sauna that will be available for eco-friendly overnight stays.
Made from black painted native spruce, the cabin operates off the main electricity grid, with solar panels on the roof to provide electricity.
The simple gabled cabin is accessed by a narrow wooden deck that forms a bridge over the rocks between the end of the forest and the door.
Another door opens on to a wooden deck facing the sea. A wide window has unobstructed views of the landscape.
Inside are a kitchen area and bathroom with a shower and dry toilet. Space-saving furniture folds down from the wall when needed to maximise the use of space in a minimal set-up. Birch plywood doors can be used to hide the kitchenette from view.
As well as solar panels for electricity, the cabin has a closed-loop water system to minimise water waste from the shower and sink.
"The purpose of Majamaja is to show how small-scale architecture, combined with green technology, can compensate for big volumes and centralised on-grid systems," said Pekka Littow.
"Majamaja offers dwellers an opportunity to disconnect from daily routines and an educational eco-living experience, yet close to the hustle and bustle of the city."
Located in Vuorilahdenniemi, the cabins are just a 30-minute bike ride from the centre of the Finnish capital.
Helsinki is set on a peninsula and surrounded by the sea on three sides and there are 330 islands in its archipelago. Majamaja is part of the City of Helsinki's Maritime Strategy 2030, which aims to invest in making the island chain a popular tourist destination while preserving the natural environment over the next decade.
Last year, Helsinki launched an app called Think Sustainably that serves as an environmentally conscious city guide for residents and tourists alike.
More off-grid cabin designs for islands include an artist's retreat in an ancient olive grove in Mallorca and a holiday home on an island off of Tasmania that features an outdoor deck with a sunken bath.
Photography is by Marc Goodwin.