It was a crisp autumn day, perfect for exploring the mysteries of ruins. This would be a home-grown adventure, just a short drive out River Road from Bethesda. I’d take a left turn at Poole’s General Store onto a dirt road and drive to its end.

I prepared myself mentally. As with any adventure—especially those involving ruins—you never know what ghosts you will stumble upon, or even if you will return unscathed.

Leaving my car, I continued on foot. In the distance I could see the river. Then, through a screen of trees and vines, I made out massive walls of reddish stone. It reminded me of a castle I had once seen in France, a memory that stirs me to this day.

Stone for a nation’s capital. This was the Seneca Stone Cutting Mill, once an integral part of Washington, D.C.’s early history. Just as Italy’s cliffs of Carrera supplied the marble for ancient Rome, the mill and the nearby Seneca sandstone quarry produced some of the most notable buildings and structures of our nation’s capital.

I had already learned something about this site thanks to materials from the Montgomery County Historical Society library gleaned by a local historian.

For one, I learned that architect James Renwick had come here in the late 1840s to select Seneca sandstone for the Smithsonian Castle. Shortly after, engineers put in their orders for stone to build the Cabin John Aqueduct (now bridge), which for the next 40 years would be the longest masonry arch structure  in the world.

The Seneca quarry and mill supplied stone for the Library of Congress as well as for many other post-Civil War buildings in Washington. In 1973 the site won a listing in the National Register of Historic Places.

From mules to jets. The stone has a distinguished geological pedigree as well. It was formed in the Triassic geologic period, when the dinosaurs made their first appearance. Initially soft and easy to work, it hardens with prolonged exposure to air.

As I entered the mill a jet roared overhead on its approach to Dulles. In the 19th century the air would have rung with the hammers of men prying reddish monoliths from the nearby hillside. Stone-laden cars drawn by mules rumbled over a narrow gauge railroad track to the mill.

I sat on the ledge of a monumental window. Before me was the channel where water from the canal―and ultimately the river―turned the great wheel, which was later replaced by a more efficient turbine. Systems of belts and pulleys transferred the power to the machinery.

I could imagine the harsh rasp of steel slicing into the stone. Gangs of men shouted over the din. They probably also took a few nips during the course of the day. Nearby I found the remains of a thick-walled bottle bearing the words “HALF PINT.”

Workmen sent the finished stones down the canal, passing through locks that in some cases were themselves made of Seneca sandstone. In 1871 alone, 850,000 tons of stone took this route.

Then, in 1900, the mill went silent. People no longer wanted red stone buildings, and anyway, the best of the stone had been used up.

Hair trigger doorway. I continued exploring as the mute walls grew dark in as the sun lowered to the horizon. In a doorway I saw where the massive stone lintel barely made contact with the stone providing support. It was like the sear and trigger on a rifle—one pull and it would all come crashing down.

Elsewhere, walls had buckled under the impact of fallen trees and limbs. Only piles of stone remained. The graffiti on some of the walls seemed a minor insult compared to the fierce neglect suffered by this noble building.

It was now dark and I felt a premonition that I had stayed too long. A barred owl hooted up the river. I hurried out, tripping over stones and tearing my clothes on the wild roses, their thorns grasping at me like velociraptor claws.

Climbing over a crumbling wall my foot slipped. As I hurtled down I could see the history of this place flash before my eyes. Now, just like the mill, I was down, cut and bruised, but not completely out.

As I write this, my shins are healing. But what about the mill? Can its decline be halted?

Attempts to save this historic structure have been few and inconclusive. One proposal made at the time of the 1976 U.S. bicentennial called for stabilizing the mill ruins, providing interpretative displays, and improving access to visitors. But as I could see, these plans had come to nothing.

A living ruin. I’ll keep returning to the mill. On each visit I’ll see that yet another tree has toppled into a fragile wall, more stone blocks that have crashed into the bushes and thorns below, more graffiti and discarded beer cans. Part of me wishes that the mill could be restored and turned into an open air museum. It would be a fine place for bicyclists to stop and eat their lunch or for teachers to take classes to learn how learn how people worked and made their living not so very long ago.

But another part of me is content to see it crumble away, stone by stone, enacting in reverse the process by which it was originally built. For so long as the old mill changes, it remains a living structure, its stones originally taken from this same place and now returning to from where they came.

It’s just that on future visits I’ll remember to leave before the owl calls.