This story originally appeared on Grist and is part of the Climate Desk collaboration.

It’s a sunny October day on the outskirts of the west German town of Bottrop. A quiet, two-lane road leads me through farm pasture to a cluster of anonymous, low-lying buildings set among the trees. The highway hums in the distance. Looming above everything else is a green A-frame structure with four great pulley wheels to carry men and equipment into a mine shaft. It’s the only visible sign that, almost three quarters of a mile below, Germany’s last hard coal lies beneath this spot.

Bottrop sits in the Ruhr Valley, a dense stretch of towns and suburbs home to 5.5 million people. Some 500,000 miners once worked in the region’s nearly 200 mines, producing as much as 124 million tons of coal every year.

Next year, that era will come to an end when this mine closes. The Ruhr Valley is in the midst of a remarkable transformation. Coal and steel plants have fallen quiet, one by one, over the course of the last half-century. Wind turbines have sprung up among old shaft towers and coking plants as Germany strives to hit its renewable energy goals.

But the path from dirty coal to clean energy isn’t an easy one. Bottrop’s Prosper-Haniel coal mine is a symbol of the challenges and opportunities facing Germany—and coal-producing states everywhere.

Around the world, as governments shift away from the coal that fueled two ages of industrial revolution, more and more mines are falling silent. If there’s an afterlife for retired coal mines, one that could put them to work for the next revolution in energy, it will have to come soon.

The elevator that carries Germany’s last coal miners on their daily commute down the mine shaft travels at about 40 feet a second, nearly 30 miles an hour. “Like a motorcycle in a city,” says Christof Beicke, the public affairs officer for the Ruhr mining consortium, as the door rattles shut. It’s not a comforting analogy.

The brakes release and, for a moment, we bob gently on the end of the mile-and-a-half long cable, like a boat in dock. Then we drop. After an initial flutter in my stomach, the long minutes of the ride are marked only by a strong breeze through the elevator grilles and the loud rush of the shaft going by.

When the elevator finally stops, on the seventh and deepest level of the mine, we file into a high-ceilinged room that looks like a subway platform. One of the men who built this tunnel, Hamazan Atli, leads our small group of visitors through the hall. Standing in the fluorescent light and crisp, engineered breeze, I have the uncanny sense of walking into an environment that humans have designed down to the last detail, like a space station or a submarine.

A row of hydraulic presses displayed at the Mining Museum in Bochum, Germany. Amelia Urry

A monorail train takes us the rest of the way to the coal seam. After about half an hour, we clamber out of the cars and clip our headlamps into the brackets on our hard hats. It is noticeably warmer here. There is a sulfurous smell that grows stronger as we walk down the slight incline toward the deepest point of our day, more than 4,000 feet below the surface, and duck under the first of the hydraulic presses that keep the ceiling from collapsing on us.

Because this seam is only about five feet high, we have to hunch as we move through the tunnel of presses, stepping through deep pools of water that swallow our boots. The coal-cutting machine is stalled today, otherwise it would be chewing its way along the 310-yard-long seam, mouthparts clamped to the coal like a snail to aquarium glass. The coal would be sluiced away on a conveyor belt to the surface, and the hydraulic presses would inch forward, maintaining space for the miners to work.