Discerning food lovers are being served salted salmon, veal tenderloin, snails cooked in Pernod and apple crumble in the "pop-down" restaurant in a limestone mine in the small, southern town of Lohja (LOU-ya), 60 kilometres (40 miles) west of Helsinki.
A four-course evening meal costs €128 ($160), including drinks and transportation from Helsinki to the mine and back.
In major cities around the world "pop-up" restaurants — temporary eateries often located in underused kitchens — are allowing young chefs with experience to experiment without risk of bankruptcy.
But Finnish chef Timo Linnamaki said the idea of preparing food down a mine was all part of being close to the earth.
"'Pop-down' is such a unique idea that I just had to do it," Linnamaki said Monday, a few hours before the first guests arrived. "It's great working down here because you are totally cut off from the world, so nothing distracts from the cooking."
Eerie blue lights cut deep shadows into the ceiling of the large, dim, underground cavern, a former smithy where drills were hammered to dig into the bowels of the Earth.
Olli-Pekka Jantti, a computer retailer from Helsinki, said his meal there was superb.
"The food was absolutely delicious," Jantti said, after supping on starters of vendace —a small local fresh-water fish — snails and berries.
"What I liked was that the theme of the evening was the earth, and being so deep down you really felt you were somewhere very different, very strange."
The 115-year-old mine goes down to a depth of 380 metres (1,250 feet) where limestone is still mined, mainly for the chemical industry.
Linnamaki, whose restaurant Muru — "crumb" in Finnish — won this year's gourmet title in Finland only two years after it opened, says the experience of working down in the gloomy depths has inspired him to search for new challenges.
"Certainly it's the weirdest place I have cooked," he said. "It could be difficult to find something on par."
The 64-seat restaurant, with long, shiny wooden tables lit by candles, is expecting brisk business. Linnamaki said it is fully booked until the experiment ends on Sept. 29.
"We'll be underground Monday to Saturday. On Sundays, we pop up to sleep," he said.