Sanandaj stands in the Zagros highlands of western Iran, capital of Kurdistan province and the main city of Iranian Kurdistan, west of Hamadan across the mountains and south-west of the rug town of BijarSee in the carpet dictionary. The older name of the place is SennehSee in the carpet dictionary, also written Senna or Sehna, and while the map now says Sanandaj the carpet trade never followed the change: rugs from the Kurdish weaving villages in and around the city are still bought and sold everywhere as Senneh. Both names describe the same place, so a rug offered as Senneh and a rug offered as Sanandaj come from the same hills.

Weaving here is village work, which in Persian rug terms is a precise category rather than a vague one. The weavers are settled in one place and work in a semi-structured setting, without the full paper cartoons a city workshop follows, but with far better access to good woolSee in the carpet dictionary, tools and dyes than a migrating tribe can carry with it. The result sits between the two: more disciplined and more consistent than tribal weaving, looser and more personal than a rug made to a designer's blueprint. Senneh rugs are among the most meticulous examples of that middle ground.

The foundation is what sets these rugs apart, and it is the first thing to look at. Senneh rugs are single-weftedSee in the carpet dictionary: a single weft thread crosses the warps, a row of knots is tied on top of it, another single weft crosses back, and so on, where a double-weftedSee in the carpet dictionary rug lays two weft shots between every row of knots. Turn one over and those single wefts show between the knot rows as a fine zigzag of white dots, a pattern that is easy to recognize once you have seen it. Single wefting is standard practice across the greater Hamadan area, so Hamadan, KarajaSee in the carpet dictionary and Mehraban rugs are built the same way, as is much Kurdish tribal and BakhtiariSee in the carpet dictionary village weaving.

Fewer weft passes mean a thinner, flatter, more pliable rug with a clearly legible back. That is worth knowing, because the other famous weave of the same province pulls in exactly the opposite direction. Bijar, less than a hundred kilometres to the north-east, is double-wefted and known as the iron rug of Iran, its weavers keeping the wool damp as they tie so that weft and knots can be pounded down with enormous force. Two Kurdish towns, two opposite structural philosophies: a Senneh lies close to the floor and drapes easily, while a Bijar behaves like a slab.

A long-standing confusion is worth clearing up at this point. The asymmetric knot used across most of Persia is variously called the Persian knotSee in the carpet dictionary, the Farsi knot or the Senneh knot, and many descriptions assume that a Senneh rug must therefore be tied with it. It is not. These rugs are woven with the symmetric knot, also called the Turkish or Ghiordes knotSee in the carpet dictionary, the knot found in Turkey, the Caucasus and the Turkish and Kurdish areas of north-western Iran. The knot carries the town's name; the town's own rugs use the other one.

That choice shapes what the rugs look like. The asymmetric knot allows finer detail, higher achievable knot counts, a softer handle and flowing curvilinear drawing. The symmetric knot, one of the oldest in use, grips the warps evenly and lends itself instead to firm, clearly drawn geometry, and Senneh shares that column with Tabriz, Bijar, HerizSee in the carpet dictionary, village Hamadan and tribal Bakhtiari. Village weaving as a class is knotted more finely than tribal work and less finely than a city workshop, and Senneh belongs in that band. DensitySee in the carpet dictionary on its own is in any case a poor measure of quality, as the famously long-lived Heriz rugs demonstrate.

Most Senneh rugs are geometric in design: a geometric medallionSee in the carpet dictionary on an open field, or a geometric allover repeat running edge to edge. BotehSee in the carpet dictionary and herati fields are found as well, and when a buyer wants a geometric pattern in a smaller rug this is one of the standard places to look, alongside QashqaiSee in the carpet dictionary, Zanjan, the weaves of Iranian Azerbaijan and Caucasian Kazak. The drawing is precise rather than florid. The pleasure of a good Senneh lies in how cleanly the figures are set out, not in how much detail has been crowded into them.

Herati, the second design most associated with the town, is also called the mahi or fish pattern, mahi being Farsi for fish. A small diamond encloses a flower or rosetteSee in the carpet dictionary and curved leaves ring it, and it is the shape of those leaves that suggested a fish and gave the pattern its other name. The unit repeats across the field, either as an allover or set around a central medallionSee in the carpet dictionary, and it takes its name from HeratSee in the carpet dictionary, the city in present-day Afghanistan where it originated. Tabriz, Bijar, Hamadan and Zanjan weavers draw it too, so on a Senneh it is the handling rather than the motif that identifies the rug.

Boteh, the other recurring motif, is the teardrop with a bent tip that Europe borrowed and renamed paisley after the Scottish mill town that printed it. The Farsi word means a budding flower or plant, and in Persian culture the figure stands for growth and regeneration. On a Senneh it usually runs as an allover, rows of small angular botehs covering the whole field, which reads as quiet texture from across a room and as a hundred separate small drawings when you stand over it.

Color follows a consistent scheme. Fields are usually dark red, dark navy or brown, occasionally beige, and the pattern is picked out in yellow, red, light green, orange and white. The effect is deep rather than bright: a dark ground carrying small, clear highlights. A field that dark hides the traffic a hallway or a doorway brings, while the light outlines keep the drawing readable from across the room, and that combination is a large part of why the weave sits comfortably in rooms that already have plenty of color in them.

Materials are straightforward: a cotton foundation and a wool pileSee in the carpet dictionary. The cotton warps hold their length and keep the rug square, while the wool carries the color and takes the wear. Sizes run small to medium, with runners a staple of the region, so the natural homes for a Senneh are a hallway, the side of a bed, a study, or anywhere a larger carpet would overwhelm the room. Antique pieces of about 1.5 by 2.1 metres sit at the top of the usual range; room-filling Senneh carpets are the exception rather than the rule.

What to expect from one in use follows directly from the construction. A single-wefted rug on a cotton foundation is light for its size, easy to lift, roll and turn, and content under furniture or behind a door with little clearance. On hard floors it wants a thin underlaySee in the carpet dictionary, since a flat rug slides more readily than a heavy one. These are rugs bought for the discipline of the weaving and the clarity of the drawing rather than for opulence, and the back of a good one, with its rows of white specks, tells you as much about the piece as the front does.

A Persian rug is an Iranian rug — a rug hand-knottedSee in the carpet dictionary in Iran — and the tradition behind it is the oldest documented anywhere. The earliest surviving carpet, the Pazyryk rugSee in the carpet dictionary, was found preserved in a frozen burial mound and dates to the fifth century BC — roughly 2,500 years ago — and it is already accomplished work, not a beginner's craft. What began as warm, hard-wearing floor coverings for tribal households grew, over those centuries, into the art form that every other rug-weaving country has borrowed from.

Two later chapters shaped what a Persian carpet looks like today. Under the Safavid dynastySee in the carpet dictionary, from 1501 to 1732, the court promoted weaving alongside painting and calligraphy, and the workshops of Tabriz, HeratSee in the carpet dictionary, Kashan and Kerman produced the masterpieces that now sit in museums. This is when the great central medallionSee in the carpet dictionary appeared, and when designs grew elaborate enough that a separate designer — often a miniature painter — drew the pattern onto a cartoon for the weaver to follow. The second chapter came in the nineteenth century, under the Qajar dynastySee in the carpet dictionary, when production reached its historical peak, exports to Europe and America boomed, and the workshop industry whose descendants still weave today took its modern shape.

The trade sorts Persian rugs into three families. City rugs — Tabriz, Kashan, Kerman, Nain, Isfahan — are woven in workshops from a drawn design, carry the highest knot densities and come in the widest range of colors, sizes and patterns. Village rugs such as HerizSee in the carpet dictionary, BakhtiariSee in the carpet dictionary and KarajaSee in the carpet dictionary sit in between, mostly geometric and largely woven from memory. Tribal rugs — Baluch, TurkomanSee in the carpet dictionary, QashqaiSee in the carpet dictionary, each named after the people who weave it — are made on small portable looms, so they run smaller, and their bold geometric drawing comes from the weaver's own head rather than from paper.

The design vocabulary draws on a deep stock of motifs: Shah AbbasiSee in the carpet dictionary palmettes, flowing arabesques, the small repeating Herati patternSee in the carpet dictionary, medallions, garden and tree-of-life compositions. These combine with regional habits into styles a practised eye can place at a glance, from the bold geometric medallions of Heriz to the fine curvilinear florals of Isfahan.

The classic palette is built on natural dyes: madderSee in the carpet dictionary reds, indigo blues, saffron yellows and the soft whites of undyed woolSee in the carpet dictionary, settled into combinations refined over centuries. Natural dyes age gracefully, mellowing into the patina that older rugs are prized for, and slight shifts of tone between dye batchesSee in the carpet dictionary — the effect called abrashSee in the carpet dictionary — are a mark of small-batch natural dyeing, not a flaw.

The pileSee in the carpet dictionary is almost always woolSee in the carpet dictionary, and in a Persian wool rug the wool itself decides much of the quality. The best fleece comes from high-altitude flocks, where it grows thicker and richer in natural oils; spring-sheared wool beats the autumn clip, and hand-spun yarnSee in the carpet dictionary gives a finer, softer thread than machine spinning. Fine pieces add silk highlights to a wool pile, and at the very top sits the Persian silk rug, woven in pure silk. Foundations are usually cotton in city weaving, wool in tribal and older pieces, silk at the very top of the range.

Every knot is tied by hand, one at a time, in one of two forms: the asymmetric Persian knotSee in the carpet dictionary, usual in central and eastern Iran, or the symmetric Turkish knotSee in the carpet dictionary, common in the north-west ever since Seljuk weavers introduced it in the eleventh and twelfth centuries. A large rug holds in the region of two million knots and can occupy a weaver for about a year.

Knot densitySee in the carpet dictionary is the figure newcomers fixate on, and the finest silk-foundation pieces do reach as much as 1,000 knots per square inch. But densitySee in the carpet dictionary only matters as far as the drawing demands it: a curvilinear Isfahan needs a fine weave to stay sharp, while a geometric Heriz is famously durable at a modest count. Material, symmetry, color harmony and condition say more about quality than any single number.

Persian carpets settle into modern rooms as naturally as classical ones, as a focal point in a living room, a foundation under a dining table or a quieter accent in a bedroom. Care is undemanding: gentle vacuuming without a rotating brush, an occasional turn for even wear, and a professional wash about every five years — sooner in a hallway or entrance, less often in a quiet room.

A hand-knotted Persian rug tends to outlast its owners. Pieces a century old regularly survive in fine condition, their colors settled and their pile supple, often looking better than when they left the loomSee in the carpet dictionary. A well-chosen, well-kept rug holds its worth and passes down as a family heirloom rather than being replaced — which is precisely what the knots, the wool and the dyes were always for.