LI stars in 'Downton Abbey' creator's new HBO series 'The Gilded Age' 

Driving down Round Swamp Road in Old Bethpage — or better still, walking — it's possible to get a glimpse of old Manhattan, circa 1882. In the summer, woods shroud the site just to the east of the Museum of American Armor, but right about now, just behind the museum parking lot and an earthen berm, the edifice arises: A Gilded Age mansion on the west side of a re-created 61st Street, and, to the east just out of line of sight, a row of brownstones.

This is where HBO's "The Gilded Age" (launching Monday at 9 p.m.) filmed in 2020 and wrapped last summer. It's a little piece of Hollywood in your backyard, or, if you happen to live on nearby Kingswood Drive or Willow Road, this piece of Hollywood literally is in your backyard.

Lots of TV shows shoot on Long Island, but none quite on a scale like this; the voluptuous interior of that aforementioned mansion, by the way, fills an entire soundstage at Gold Coast Studios in Bethpage. Dozens of buildings, or their exteriors, as well as a Potemkin village train station and ferry terminal, went up on this site two years ago. There they will remain, perhaps for years or seasons to come.

Gary Lewi, vice president of the American Armor Museum, who ran interference for the production team when they decamped here, calls the set "nothing less than extraordinary."

He's not wrong. Even by real Hollywood back lot standards, this place would be impressive. It's an immaculate reconstruction of a bygone world, meant to appear as if it was just minted yesterday, with the sharp edifices of these buildings lined, as it were, with gold.

This was (or is) the Gilded Age, after all. Gold is a requisite.

HBO declined to offer a tour of the site because it was mothballed early last summer after production wrapped. But it's easy enough to see in the extended trailer, released in December. "New York is a collection of villages," says Christine Baranski's Agnes Van Rhijn — think Old Money dowager with stiff upper lip — in voice-over. "The old have been in charge since before the Revolution until the new people invaded."

Ah, yes, those "new people," specifically fictional railroad baron George Russell (Morgan Spector), and his hyper-ambitious wife, Bertha (Carrie Coon.). To Agnes, they are vulgar arrivistes with too much money who are desperate to claw their way into the frosty, rarefied upper reaches of Manhattan society. They are the ones who built that garish mansion across the street from her tasteful (or rather faded) Old World beauty.

With a few exceptions, virtually every scene in that 2:17 trailer was filmed on this lot or at Gold Coast Studios six miles away.

Last summer, "there were occasions when they were setting up for the 1890s, and we were running [World War II-era] tanks in the other direction," says Lewi. "You were looking around for Rod Serling."

Dozens of TV shows, of course, have filmed on Long Island over the years, from "The Affair" to "Z: The Beginning of Everything" (about Zelda Fitzgerald). They come here for the views (mostly water) or atmosphere (in a word, the Hamptons.) They set up their cameras, take their pretty pictures, then disappear — until they need more pretty pictures.

For a complex set of reasons, "The Gilded Age" has been different. When "Downton Abbey's" Julian Fellowes and longtime production partner, Gareth Neame, decided to pursue a period drama about the Roaring '80s — the 1880s — they knew they needed proximity to New York City, cradle of the Age, but also to some of the remnant glories of the time period, a few of which still stand on Long Island and elsewhere, including Jay Gould's vast white elephant, Lyndhurst, in Tarrytown. They also needed access to older homes, like Lawrence's Rock Hall (1767), which can also be seen in that trailer.

Moreover, they needed a place that could double for Central Park circa 1882, the year the so-called Triple Palaces were built along Millionaire's Row on 5th Avenue. This obviously meant there couldn't be skyscrapers looming over trees. The landscape also needed to be relatively flat, with mature trees. The location scouts quickly settled on the grounds of Old Bethpage Village Restoration for that purpose.

David Crockett, executive producer as well as line producer on "The Gilded Age" — which means, among other things, that he's the boss of all aspects of the physical production — said in a recent phone interview that "we knew there would be a bunch of places here and in some respects, more of it would be filmable" than elsewhere in the country, with the exception of Newport, Rhode Island, which also gets an extensive close-up in "The Gilded Age."

"But you also are reminded that it is set a hundred-and-forty years ago. The challenge was not only finding a building that exists from 1880 or 1900, but asking whether the interior and exterior look structurally the same as they did then. They can't look antique — but modern."

He added, "our story is really an old money/new money story, at 61st and 5th Avenue where the Old Money Van Rhijns have lived and grew up and then comes 1882, and a place goes up across the street that's no different from the Doris Duke [the Benjamin N. Duke House at E. 82nd Street] or Frick [E. 70th] mansions that went up on 5th Avenue at the time. There was no finding that sort of place to shoot so we quickly chose to build early on. "

For the interior of the Russell mansion, HBO and production company Universal TV contracted with Gold Coast, which has the largest sound stage on the east coast. (Apple +'s "Dickinson," which recently wrapped, was also partly filmed there.) The exterior would be the tricky part, however.

After the production settled on Old Bethpage, Crockett and HBO began negotiating with Nassau County to build a set on 6.25 acres of land adjacent to the museum — land that once crawled with M18 Hellcats or M48 Pattons. Lewi and the museum board agreed to move the tanks further south and then, in late November, 2019, HBO worked out a deal paying the county $600,000 in annual permit fees for the land. It also promised jobs, educational "opportunities" at local schools, and a plan to build athletic fields on the site when "The Gilded Age" goes off the air.

During production last spring, then-Nassau County Executive Laura Curran went to the completed set, telling Newsday that "I visited not too long ago [and] it's really stunning." Besides that re-created slice of Manhattan, what Curran saw and passerby still can are huge green screens. Those are used to digitally re-create scenes that a set, no matter how sumptuously built, ever could. (For one of those special effects scenes, says Crockett, the producers even created the turbulent waters of the Hudson River.)

What happens when "The Gilded Age" ends, as all shows must? "Hopefully we'll be back at Old Bethpage and Gold Coast for season two, God willing," says Crockett, then adds, "God willing, and if COVID subsides a little bit."

Lewi meanwhile hopes his new neighbor sticks around. "While I'm not an expert on construction, they have clearly created a back lot that will last years to come and will accommodate many seasons [of the 'The Gilded Age']."

He adds, "it could easily be repurposed years from now, long after a successful series run. This is an asset that's unique to New York, and certainly unique to Long Island."