There are no natural caves to dive in Finland.

So Finnish cave divers found another way underground.

Ojamo looks like a small lake in a forest outside Helsinki. But beneath the
surface is a flooded limestone mine: kilometers of straight tunnels, rusted
rails, concrete pillars and shafts descending level after level into darkness.

The mine was abandoned in the 1960s.

The pumps were turned off.

And the water rose.

Today, divers swim through tunnels built by miners more than a century ago.
Some passages run beneath Lake Lohjanjärvi, where an old concrete structure
still supports the roof beneath the weight of an entire lake.

Divers call that place the Gates of Hell.

But Ojamo is also where generations of Finnish technical divers learned to
survive under a ceiling. Divers trained here have gone on to some of the most
dangerous cave dives in the world — including major rescue and recovery
operations.

And deeper inside the mine is something no diver has seen in decades.

The old maps say the main shaft reaches 250 meters.

The deepest recorded dive reached 160.

Nearly 100 meters of flooded mine remain between the deepest explored point
and the bottom shown on maps drawn before the mine was abandoned.

Nobody knows exactly what 60 years underwater have done to what lies below.

This is Ojamo: the flooded mine beneath a Finnish forest that was built to be
forgotten.

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#DeepDiving #Underwater #AbandonedMine #DivingDocumentary #ExtremeDiving
#DarkHistory #Exploration