A delicate revolution that left the commoners out of pocket and forced the gentry to fish for compliments

This handsomely produced book, with its modish see-through dust-jacket and wealth of illustrations taken from intensely aristocratic prints of the 1720s, is seriously judgemental of the class it describes.

Dianne Harris, its author, is associate professor of landscape architecture and architecture at the University of Illinois, Urbana-Champaign. She weighs up the social, political and economic performance of the 18th-century aristocracy of the Lombard duchy of Milan and finds it wanting, but she expresses interest rather than condemnation.

She suggests that selfish conservatism and failure of aesthetic invention allowed the 12 great families, all with country villas and estates, to sentence themselves to oblivion.

In 1705, when the duchy became a colony of the Habsburg empire after the victories of Prince Eugene, the native Italian aristocracy not only retained its estates, but still held, under a German governor, all the offices of state. Meanwhile, the province, because of the extraordinary fertility of its soil, became known as "The Indies of the Court of Vienna", a milch cow for tax collectors, serving Austria as Mexico and Peru served Spain.

At this point, when Vienna was intent on squeezing as much tax money as possible out of its new colony, the "reforms" of "an enlightened autocracy" were instituted.

The first, and minor, reform was social - the introduction of a French-style salon system, not in the drawing rooms of town houses, which remained private, but in the boxes of the multitiered Teatro Ducale. In the evening, ladies received their friends there from 8.30pm to midnight, and social status became acutely visible, dependent on the height of the tier and the proximity of a box to the apex of the curve where the governor sat.

The second, and major, reform was that of the cadastral survey. This was set up after 1706 and pressed through with legendary but very real German efficiency.

The survey mapped out, in delicate shades of water-colour, the precise agricultural usage of every parcel of land, together with its ownership, resulting in an entirely fair exaction of an entirely unfair level of taxation. There were no exemptions, and the aristocracy was ranked bureaucratically alongside commoners.

Rice paddies were to 18th-century Lombardy what atomic power stations are to us today: economically useful, but a frightening source of disease - malaria in this case. They were all washed in green on the cadastral maps and had, by law, to be at least 5 miles away from any large centre of population. The unfortunate risaroli who tended them were the lowest of the low, bound in virtual slavery by the terms of their contracts and with a short life expectancy. It would be necessary to turn to the mines and factories of the industrial revolution to find an English equivalent.

As a counter to the vulgar egalitarianism of the cadastral maps, the aristocracy turned to the artist-engraver Marc'Antonio Dal Rey's mistitled Ville di delizie ( Villas of Delight ), published in 1726- and 1743. These prints were grander, more exquisitely delineated and socially observant crosses between our own Britannia Illustrata by Leonard Knyff and Jan Kip (1707) and Colen Campbell's three volumes of Vitruvius Britannicus (1715, 1717 and 1725). It is by an ingenious exegesis of the Villas of Delight , held up against the harsh realities of the cadastral maps, that Harris projects her whole subtle analysis of a corrupt, self-satisfied society.

Where the English gentry was obsessed with protecting its game, Lombard lords were intent on preserving the carp in their ornamental ponds. Dal Rey illustrates gentlemen active with rod and line by their ponds. He also draws folk peering forlornly into the estates through iron gates. Commoners were not welcome unless, as at Niguarda, all 12 formal parterres were really vegetable plots.

Meanwhile, architecturally, the villas look like ornamented tenement blocks, even though the neighbouring Veneto was alive with Palladio's inventive adaptations of the villa-farm to classical temples.

Judgemental comparisons may be invidious, but Harris might have risked the point that, while only four of Dal Rey's villas survive, in England - where lords married into money, opened their grounds to the public and even, at Stourhead, built a hotel to accommodate their garden visitors - stately home visiting remains a flourishing national pastime. Until someone comes up with a better system, the hereditaries still retain a toe-hold on the legislature. A welcoming cheerfulness can pay dividends to landowners.

Timothy Mowl is reader in architectural and garden history, University of Bristol.