It will be 1,380 feet under and cost roughly $4 billion to build. But Finland is banking on its most expensive 'graveyard' to address its most pressing issue: what to do with the 5,500 tonnes of nuclear waste?
The tiny island of Olkiluoto, already home to one of Finland's two nuclear plants, will be the burial ground for all the nuclear waste in a tunnelling project which will start in 2020 and sealed shut by the 2120s.
According to the International Atomic Energy Agency (IAEA), Finland has four operational nuclear power reactors while another one is under construction. It generates 33.73 percent of its total electricity through these power plants.
To put the figure into perspective, France produces 76.34 percent of its electricity through nuclear plants and tops the list of countries which rely on nuclear energy to supply ‘at least one third of their total electricity’.
That amounts to double the waste and adds to the growing problem of disposing nuclear by-products since the first plants were built in the 1950s.
Many countries have kept the waste in temporary storage above ground, but Finland is aiming to become the first country to bury it for good.
"This has required all sorts of new know-how," Ismo Aaltonen, chief geologist at nuclear waste manager Posiva, which got the green light to develop the site last year, was quoted as saying by AFP.
The project was initiated in 2004 and was led by a team of geologists tasked with studying the suitability of the bedrock.
At the end of 2015, the government issued a construction license for the network of tunnels called Onkalo -- Finnish for "The Hollow".
At present, Onkalo consists of a twisting five-kilometre (three-mile) tunnel with three shafts for staff and ventilation. Eventually the nuclear warren will stretch 42 kilometres (26 miles).
The temperature is cool and the bedrock is extremely dry -- crucial if the spent nuclear rods are to be protected from the corrosive effects of water.
Safety is at the top of the agenda for the experts linked with the project. Hence the 100,000-year plan.
The layers with which the nuclear waste will be encapsulated before being stowed away in the tunnels are multifold. A coffin within a coffin, if simplified.
First, the spent nuclear rods will be placed in iron casts, then sealed into thick copper canisters and lowered into the tunnels.
Each capsule will be surrounded with a buffer made of bentonite, a type of clay that will protect them from any shuddering in the surrounding rock and help stop water from seeping in.
Clay blocks and more bentonite will fill the tunnels before they are sealed up.
The method was developed in Sweden where a similar project is under way, and Posiva insists it is safe.
But opponents of nuclear power, such as Greenpeace, have raised concern about potential radioactive leaks.
"Nuclear waste has already been created and therefore something has to be done about it," said the environmental group's Finnish spokesman Juha Aromaa.
"But certain unsolved risk factors need to be investigated further."
Among the major concerns of environmentalists is the unpredictability of nature and what the climate may transform into in a 100,000 years’ time. They are not ruling out another ice age.
For now, Olkiluoto's current residents have grown used to living next door to two nuclear reactors, with a third under construction.
Local vegetable farmer Timo Rauvola was sanguine about the plans for a nuclear burial ground.
"Personally, I believe that when (the waste) is placed deep down there with care and expertise, it is better than how it is now around the world -- placed wherever."