"Highclere Castle is probably the most important character in the show," says Hugh Bonneville, in a promotional video about "_blankDownton Abbey," the popular period drama that finishes _blanka four-episode run on PBS on Sunday evening. The Edwardian upstairs-downstairs drama, starring Bonneville as the upper-crusty earl of Grantham, looks at the lives of the privileged elite and their servants at the imaginary Downton Abbey. It was filmed at Highclere Castle, a mansion still occupied by the eighth earl of Carnarvon.

No, it's not the most important character in the show. It's a house, and like many of the stately old homes of England, its owners hire it out for just about anything (corporate events and weddings are popular). But it is a very sumptuous setting for a drama that has proved addictively entertaining. And if one wanted to sum up everything that is delicious and ridiculous about this program, written by Julian Fellowes ("_blankGosford Park"), the design of Highclere is a good place to start.

On first glance, it looks just like the kind of country house that the Elizabethan elites were building near the turn of the 16th century: a brilliantly detailed, boxy, symmetrical pile bristling with delicate ornament. It has much of the whimsy and lightness of the celebrated houses designed by Robert Smythson in the mid-to-late 16th century. Like other buildings of the period, it has long, vertical windows with delicate mullions. By pushing windows out to the plane of a building's external wall, architects of this era created a fantasy of lightness in stone. The thickness and heaviness of the masonry disappears, and the structure feels almost like a tent of glass and stone pitched on a plane of green grass.

But it is really an elaborate act of fakery, a 19th-century product of early Victorian extravagance. In 1838, the third earl of Carnarvon hired Charles Barry, the same architect who (with Augustus Pugin) designed the neo-Gothic Houses of Parliament on the Thames in London, to completely refashion an existing and not very interesting Georgian-style country home in Newbury, England. Barry redressed the building, added tower elements and slathered the whole thing with a thick icing of period detail, and voila: The earls of Carnarvon had a house that suggested a long pedigree and hearkened back to the fantasy days of Good Queen Bess.

Or as a guide to privately owned castles bluntly puts it: "The Earl of Carnarvon wanted a house ostentatious enough to match his increasing wealth and importance." "Gaudy is Good" was one of two guiding principles of most Victorian architectural aesthetics. The other was a strongly nativist and reactionary view of architecture: the belief that only an authentic British architecture was good enough for the Empire and that the only styles that were properly British came from the glory days of the Gothic and Elizabethan eras. Britain needed an architecture "befitting her wealth and political importance," according to a 19th-century review of Barry's Houses of Parliament, and if you wanted smugness in stone, Barry was the go-to man.

To understand why, a century ago, most modern architects were fanatically united in their opposition to ornament, look to buildings such as Highclere and to the excesses of Victorian Gothic and related revival styles of the time. Re-creating a past style is fundamentally regressive, consuming huge amounts of labor and expense to create something that makes viewers wish they didn't live in their own time, but in a better, earlier one. It is wasteful and alienating. And in the case of many of the Victorian architects, it came with a deep commitment to the absurd belief that the Middle Ages were a better, more wholesome, happier era for mankind. At least in comparison with modern times, against which critics such as John Ruskin railed in torrents of florid language. Ruskin, among other things, considered iron - which was transforming transportation, architecture and industry - to be "the most fruitful source of corruption."

So perhaps it's no surprise that among the things the earls of Carnarvon were famous for was their strident opposition to the Reform Act of 1832, which expanded suffrage, and the repeal of the Corn Laws, which kept food prices high and enriched the landed gentry.

Highclere may not be the most important character in "Downton Abbey," but it is the perfect setting for a drama that, despite its rich characterization and excellent dialogue, is weirdly regressive about class. Unlike _blanka dramatization of a _blankJane Austen novel, which is a historical document of the era it satirizes, "Downton Abbey" is made up from scratch yet celebrates (perhaps unintentionally) the class system it purports to deconstruct.

While the narrative distributes the fine and ugly qualities of human nature liberally among both the upper and lower orders, it's in the nature of this kind of costume drama that no one really identifies primarily with the servants. We all want to live upstairs, in the world of the earl of Grantham and his three daughters and the elegant garden parties and afternoon teas with which the aristocracy whiles away the time between adolescence and death. Even the one mildly radical character, a chauffeur with progressive ideas, confesses to being merely a socialist, not a revolutionary. Everyone is devoted to Downton Abbey.

Seen in the background of the drama, Highclere Castle stands for the life project of the earl of Grantham, who is devoted to maintaining it as an estate, a building and a social system. The historical references of the architecture suggest that the abbey has been there for hundreds of years - that it is a long-standing product of an unshakable social hierarchy - but in fact, it should be barely 75 years old when the series begins in 1912.

Curiously, the building was not adequate for representing the "downstairs" life at the fictional abbey. According to a very chipper receptionist at Highclere castle, the house has cellars, but these are windowless and currently contain an exhibition of Egyptology. For the television drama, the servants' space, including the kitchen, were created elsewhere. In the kind of Elizabethan-era home that Barry's Highclere imitates, they would likely have been on the same floor as the main hall.

But when it comes to historical fantasy, the rules can be rigid. "Downton Abbey" needs a downstairs, because that's where servants work, at least servants seen on classy, high-end British costume dramas. Rather like the exterior of Highclere Castle, and so many revivalist buildings, there is an overstuffed and over-perfect quality to the drama on "Downton Abbey," as if the author is borrowing a bit of the best story lines from two centuries of novels. Even the gay subplot, which includes a blackmailing servant, seems borrowed from both _blankthe stories of E.M. Forster and _blankthe trial transcripts of Oscar Wilde.

Which is to say, the writing is a hodgepodge of ideas, themes and subplots already familiar from decades of "_blankMasterpiece Theatre," reconstituted for a contemporary sensibility. Authenticity matters less than surface delight. A profusion of detail substitutes for a strong central narrative. And the whole thing is packaged as history, giving legitimacy to extravagance. A better definition of Victorian architecture can't be offered.