We do know that it was fundamentally different from, and more advanced than, the rest of Western Europe. It boasted one of the medieval world's largest cities, Cordoba, which was up to 20 times larger than any other Western European capital. It had a powerful, expanding economy involved in large-scale domestic and international trade. There was probably even some mass production, of textiles and ceramics, and the agriculture was largely run to produce a market surplus - not simply at a subsistence or local consumption level, as in most other parts of Europe in the early medieval period.
Administration was also relatively sophisticated. By the ninth century, Cordoba had its own local government civil servants - the Muhtasib (in charge of regulating urban services - markets, water supplies, schools and public health protection) and the Sahib al- Shurta (the police chief charged with maintaining law and order). Islamic Spain also saw the first use of paper in Europe - and indeed it was through Spain that paper was introduced into the rest of the continent. Paper allowed for a spectacular increase in intellectual as well as bureaucratic activity.
It was through Spain that many of Aristotle's philosophical ideas were fed back into Europe, having been preserved in the Arab Middle East. Muslim Spain was, it seems, also much more cosmopolitan, and for most of the time much more tolerant, than other parts of Europe - in many ways, simply more modern.
Yet today it can be regarded as the least known of all European civilisations. Most of the documentary evidence - thousands of manuscripts - was either thrown away or destroyed by the Christians who, bit by bit, conquered Muslim Spain. And there is very little archaeological evidence. Serious Islamic archaeology in Spain is little more than a decade old. Opportunities for a thorough investigation of Spain's past - including its great Islamic heritage - are often lost because of pressure by politicians and developers.
A further impediment to discovering what life was like in medieval Muslim Spain is a consequence of Islamic culture itself. In much of the rest of Western Europe, landscapes, townscapes, castles and everyday happenings were recorded by artists. In the Muslim world, figurative art was not fashionable; indeed, it was forbidden in some periods. As a result, few visual records survive.
The Christians, furthermore, threw out not just the records but the Muslims themselves. In a savage ethnic cleansing operation, the descendants of more than half of early medieval Spain's population were forced to abandon either country or faith. Most of them were expelled, others were forcibly converted to Christianity. Still others - many of them descendants of Islamic Spain's Jewish community - were massacred. Spain's ethnic, cultural, linguistic, religious and political continuity was broken. Little Islamic Spanish culture survived. It is known that the Arabs conquered virtually the whole country in the early eighth century, and that various Muslim rulers held more than half of Spain for around 450 years. It is also known that from the mid-13th to the late-15th century, only a tiny remnant of Islamic Spain - the kingdom of Granada - survived, and that the last Muslim inhabitants of Spain were expelled in the early 17th century, bringing to a close 900 years of Hispano-Muslim culture.
But what is not known about this most remarkable of Europe's medieval civilisations far exceeds that which is. Historians do not agree on how many Muslims entered Spain in and immediately after the eighth century. Was it thousands or hundreds of thousands?
Nor do they know precisely who these people were. Were they mainly of north African (Berber) origin or a more even mix of Berbers and Arabs? Did they come with their wives and families, or as warriors?
Why did they come at all? What made them forsake North Africa? Were there agricultural or overpopulation problems, or did they want to control new lands? Had Spain become a sort of geopolitical vacuum, depopulated after the end of Roman rule? Or was the conquest simply a continuation of Muslim expansion which had already brought most of the Middle East and North Africa under Islamic rule?
Historians do not even know exactly how Muslim the country was under Islam. Bishops were allowed to function, Christianity and Judaism carried on. Some estimates suggest that by the late 10th century, up to 60 per cent of the population of the Iberian peninsula was Muslim. But it is just a grand guessing-game; the total population is variously estimated between 6 million and 16 million. Although the largest city, Cordoba, had up to 500,000 inhabitants - at least 40 times as big as medieval Rome - historians have no real evidence as to what it looked like.
Europe got many of its foodstuffs - rice, sugar cane, spinach, lemons, oranges, asparagus and hard wheat, from which pasta is made - via Muslim Spain (and to some extent Muslim Sicily). And it is from the same source that Europe gained its knowledge of star charts, astrolabes and other navigational equipment, without which the exploration of the New World would have been more difficult.
Muslim Spain was also the avenue through which much classical knowledge re-entered Europe; as did such basic technology as the vertical mill. Strangely, however, its irrigation system, using water-wheels to lift water from one level to another, was never adopted in the rest of the continent, despite massive economic advantages. Nor, indeed, was its communications system, the use of flashing mirrors to transmit messages over long distances. Chroniclers claimed that it took just 24 hours for a message to go from Egypt to Spain (about 2,300 miles). Pigeon post, using lightweight airmail-style paper, was also developed to service shorter-haul destinations.
Botanical gardening for growing medicinal herbs, the making of equipment for chemical experiments, and the art of paper-making were, however, transmitted to the rest of Europe. Luckily for our forebears, another medieval Islamic Spanish innovation, purchase tax, was not introduced to most of our continent until more recent times.
Of Islamic Spain itself, little remains except magnificent architecture, preserved in numerous castles, town walls, palaces and mosques. The Arab language has long gone from Spain, although that most famous of Spanish words, Ole, derives from the Arabic for God, Allah.
There are three places outside the Iberian peninsula where the spirit of Muslim-ruled Spain lives on. Still flourishing, mainly in Israel and Istanbul, is the culture not of the Hispano- Muslims but of the Jews of medieval Muslim and Christian Spain. Some Jewish music, ballads and romantic and political poems (one even describing the fall of Muslim Granada) have survived from Islamic Spain.
In Israel and Greece, a few hundred people still speak Ladino - the language of the Jews of Muslim Spain. Jewish merchants, scientists, even prime ministers, contributed to the success of the Moorish venture in Europe. The third place where the culture of Muslim Spain has to some extent been preserved is north- west Tunisia. There, Hispano-Muslim families, driven into exile in the 16th and 17th centuries, continue to live and flourish, fully conscious of their origins and traditions.
But perhaps Islamic Spain's most unexpected legacy lies off the north coast of the English county of Devon, where tourists can visit a small castle on the remote Bristol channel island of Lundy - a castle almost certainly used in the 17th century as a base by Muslim pirates from a pirate republic in southern Morocco.
These marauding seafarers, known in England as the Sally Rovers (because they ran the self-styled Republic of Sale, pronounced sarlay), were the last Muslims thrown out of Spain, in around 1612. They were none too keen on Christians, and are believed to have made Lundy Castle a base from which to seize unfortunate West Country Englishmen (and women) to be sold as slaves in North Africa.
For the great Islamic civilisation of Spain, this twilight destiny was tragic: exile and piracy was a sad afterlife for one of Europe's most splendid cultures.
GETTING THERE: Fly with Iberia (071-437 5622) to Malaga, return from pounds 189; Granada, return from pounds 221; or Seville, return from pounds 206 (min stay one Sat night, max stay one month, no advance purchase necessary). Fly to Malaga with British Airways (081-897 4000) from pounds 185 return (same restrictions); Trailfinders (071-937 5400) return from pounds 164. Trains to Cordoba depart every two hours from Seville and Malaga; journey times around 1 1/2 and 2 1/2 hours, return fares from pounds 4 and pounds 6 respectively. There are three trains
daily between Granada and Cordoba, journey time around 4 1/2 hours, return fares from around pounds 8. Hire a car from Avis Rent A Car (081-848 8733), Budget Rent A Car (0800 181181), or Hertz Rent A Car (081-679 1799).
TOUR OPERATORS: Magic of Spain (081-748 7575) 'pick and mix' holidays combine up to 20 centres in individual itineraries; 7 nights bed and breakfast in Cordoba from pounds 594, including flights and car hire. Mundi Color Holidays (071-828 6021) offers tailor- made fly-drive tours combining Cordoba, Granada and Seville; its 8-day Stars of Andalucia itinerary starts at pounds 495, including flights, car hire and accommodation. New Century Holidays (0326 375959) offers tailor-made city holidays to destinations including Cordoba, Granada and Seville.
FURTHER INFORMATION: Contact the Spanish National Tourist Office, 57-58 St James's Street, London SW1A 1LD (071- 499 0901, fax 071-629 4257).