If this isn't a perfect vehicle for the Coen Brothers, I don't know what is.

The car is indeed a Ford. It has obviously been disassembled, and the fuel tank is out of place, and the steering column is lying much lower than it would be in use. It has a brass radiator so is pre 1917, but has electric headlights so is post 1914, so is only about ten years old at the time of the photograph.

One of the mudguards (fenders) is at the base of the tree hiding the feet of the smiling man in the greatcoat.

It seems that tunnel building wasn't the only hobby of Dr. Dyar. According to the interesting case of Allen v. Allen, 193 Pacific Reporter 539, Dr. Dyar was also a practicing bigamist. He apparently married his second wife using the name of Wilfred Allen. His second family seemed to have lived nearby his first in Washington, DC. The question is was he digging his tunnels to connect the homes of his two families? (The reporter who broke the first story of Dr. Dyar being the source of the tunnels also found a second set of tunnels at his house on B Street.) At some point, his first wife had had enough and wanted out. This would seem to have left wide open his relationship with his second wife except that they had concocted a fictional husband who they now needed to remove from the scene. So, they loaded the kids up in a ship and went west for a quickie divorce in Reno. Unfortunately for the Allens/Dyars the judge in Reno didn't buy their story. Not sure how it all sorted itself out in the end, but I do know that the good doctor suddenly died five years after the story of his tunnels made the local papers.

I'd like to have that flashlight he's holding.
(I collect flashlights, old ones are especially cool)

But wait - there's more. In 1906 (one year after he started tunneling for exercise), Dyar secretly married Wellesca Pollack using the alias Wilfred Allen while remaining married to his first wife, Zella Peabody. The two of them had three sons, and he deeded $100,000 in property to her. Unfortunately for him, he had another hobby - writing and publishing autobiographical short stories about a character named Mr. French. In one such story, Mr. French deeded a substantial amount of property to "Flossie," until Mrs. French discovered it. That story was used against him in two highly-publicized divorce suits, Dyar's Reno suit to divorce Zella (which failed on jurisdictional grounds), and Zella's California suit to divorce Dyer (which apparently succeeded). Then, as Harrison Dyar, he legally married Wellesca, and adopted their three sons.

[Wow. Amazing. - Dave]

Washington Post, Sep 27, 1924

Mr. Dyar at first was reluctant to discuss his strange handiwork which, when uncovered, created such a mystery that theories that the tunnels had been used as a meeting place for German spies in war days were given as much attention as the police theory that they were the rendezvous of bootleggers. It had been suggested even that they labyrinth was the workshop of a gang of counterfeiters.

"No." chuckled Mr. Dyar. "The theories are all wrong. You have solved the mystery all right. I dug the tunnels. I did it for exercise. My son, Otis Dyar, who is now a man and married out in California, was a little boy when I began to dig. He used to play in the tunnels.

"In fact," he continued, "other boys played in the tunnels and while they didn't annoy me they became a nuisance to some of the neighbors. Complaints were made and I recall on one occasion Detective O'Brien investigated.

"Another time, I recall, a policeman came snooping around to look into the tunnels. I played a little joke on him. I put a clock back in the tunnel and when the policeman heard it ticking he must have thought it a time clock on an infernal machine or a smuggler's den or something."

Contractors and engineers who have viewed that part of the labyrinth which has been opened declare the bricklaying and construction of the passages generally the work of an expert artisan.

"I'm not a bricklayer," Mr. Dyar said with a laugh. "My business is with mosquitoes, moths and butterflies. I just laid the bricks on evenly; that's all."

…

Mr. Dyar said he knew nothing of the German newspapers which were found in the tunnel and which gave rise to the rumor that perhaps German spies had occupied the underground place. He pointed out that they were dated in 1917, two years after he had moved from the Twenty-first street house.

But I can't see Stan or Ollie.

The Model T has a brass-era radiator piled on the frame that was last used in 1916. The headlight are mounted in a style that started in the summer of 1915.

Interesting hobby. Some people collect stamps; some build model aeroplanes. He wanted something different.

The remains of the auto in the upper right have me wondering what model year it is. Must have been one of the first Model T's from '08.

Click to enlarge.

It's where Saddam Hussein's great grandfather hid out.

Washington got its first inkling of this subterranean network when a truck sank a wheel into one of the tunnels in an alleyway behind the Pelham Courts apartments on P Street, making the hole shown in our photo. Initial speculation centered on German spies and rum-runners. The truth turned out to be more prosaic, yet still bizarre.

They were the work of a millionaire Smithsonian entomologist named Harrison Dyar, who said he had dug them between 1908 and 1916 "for the exercise," although he clearly seemed to have a fixation on underground passages. After his newspaper interview in 1924 (below), he was found to have dug another network of tunnels around his current home on B Street (Independence Avenue). He died in 1929, though parts of his underground labyrinth were still being stumbled upon (and into) as late as 1958.

This is some sort of forgotten security/escape tunnel leading from a government building, probably dating to the time of the Civil War.

Could this be one of Dr. Dyar's creations?

a broken bottle the one guy is holding in his hand? Hard to tell, but this being 1924, it's a good chance that the tunnel has something to do with Prohibition. Ask Al Capone. Or, maybe, Geraldo Rivera.

The fellow with the pocket watch and no jacket doesn't look like he is having a good time. Perhaps, since this is the height of prohibition, that is because these hardy boys have found where he stores the hooch.

Must be an escape tunnel from a speakeasy.

Alice's favorite tea parties take place here.

Considering the year of the photo. That what they have found is either the location of a still or some bootlegger's stashing place.

Could the mysterious tunnel have anything to do with bootlegging?

So much for the Trilateral Commission's secret tunnel to sneak up on the Masons and take over their plan for world domination.

The man bending over the hole looks to be holding a broken bottle. Could this perhaps have something to do with prohibition? Maybe it was an escape tunnel from a speakeasy?

Back in the day if Jimmy came out of his underground lair and saw his shadow, it meant 6 more weeks of winter.

If it's connected to the garage in the background, I would guess it's an escape route from a speakeasy.

Every kid should wear a light colored jacket and cap when going into a hole in the ground. I'm wondering what the man is handing the boy. It almost looks like money?

Someone's smugglin' turnips!

Given that 1924 is during Prohibition, I'd bet it was an escape tunnel from a basement "speakeasy" in one of the background buildings.

Caould it be a cellar to hide illegal liquor? Looks like the fellow leaning down towards the hole is holding part of a broken bottle out towards the fellow coming up from the hle.

It looks like the piece of sheet metal was used to hide the mysterious tunnel.

Prohibition was in full swing at this point. The official looking men, the camera tripod, a broken bottle in the hand of the bull leaning over the hole. The happy expression on the face of the young man coming out of the hole. Perhaps a distillery raid?

The twenties, an alley, a tunnel. I suspect something to do with the Volstead Act.

Hey, I know! Let's get the the skinny kid with the newsie cap and light colored jacket! It'll be a hoot!

Could the man bent over the hole be holding the key?

A strong hat vibe.

"This is clearly a mystery tunnel," said D.C. Police Inspector Sherman T. Ransom, second from right in photo.

A mysterious tunnel discovered in our nation's capital! Those pesky Freemasons are at it again.

Are you sure that rabbit said this was the way to Albuquerque?

Might this have had something to do with Prohibition? The man standing over the hole is holding a broken bottle neck, and some of the participants are grinning like they've figured it out. In recent years out here in San Diego, the DEA and INS have found several "mysterious tunnels" running under the international boundary between Tijuana and San Diego. Somehow those tunnel discoveries never seem to inspire the kind of jollity seen here.

Underground railroad, or, secret distillery.

The alleyway has been blocked with a board nailed to the trees; the lantern (red, maybe) will serve as a warning at night. Also note the camera tripod.

Next to the laundry, the bones of a Model T.

The men in suits look like they may be detectives. Am I even warm?

just an forgotten old septic tank.

[What it is is what the caption says. - Dave]

It's probably an old basement from a burnt building. Burnt building debris falls into the basement and leaves voids to be discovered later.

[A plausible theory, but incorrect. - Dave]