Deep in the south of India lie the spectacular remains of one of the world's most remarkable and most forgotten civilsations. In its heyday it was one of the half-dozen greatest powers on Earth. It controlled half a million square miles - more than five times the size of Britain. And under its wing literacy and the arts flourished.
Yet today, 1,000 years later, the Chola Empire is remembered only by a handful of specialist historians. If it had been European, or had given its name to some still-surviving nation, things might be different. But despite 400 years of glory, the Chola Empire disappeared from history; a sad fate for a civilisation which was among the most remarkable produced by the medieval world.
In some ways, it was the most significant of the dozen or so empires which rose and fell during India's long, tumultuous history. It lasted some 460 years, longer than any of them. The Chola was also the only Asian empire (bar the Japanese) to have indulged, albeit briefly, in overseas expansion. It conquered Sri Lanka, the Andaman and Nicobar islands and, temporarily, parts of south-east Asia - the islands of Sumatra, Java and Bali, and the southern part of the Malay peninsula.
Most of these overseas conquests are shrouded in mystery. All that is known is that, in 1025, the Chola emperor Rajendra I dispatched an army, presumably on a large fleet, across 2000 miles of ocean to conquer the southern half of south-east Asia. The records show that he succeeded and received the submission of large numbers of cities. Some historians believe that the Cholas then simply sailed back to India, but others suspect that Chola power persisted in some form in south-east Asia for two or three generations.
Certainly, the Chola conquest contributed to a long process that had already started and which linked southern India and south-east Asia together in terms of trade and religion. The Indonesia/Malay region was a pivotal point in trade between China and India (and, indeed, the West), and both Java and Bali were largely Hindu. Rajendra's conquest was perhaps the first military expression of a more general connection which had been developing for centuries.
Closer to home, in Sri Lanka, the Cholas' overseas expansion is better documented, both in text, and in stone. Tourists today can still explore the great ruined city of Polonnaruva, founded by the Cholas as a capital for their newly conquered island territory.
But the emperor's armies didn't only head southwards. In the early 11th century, Chola forces marched almost 1000 miles through India to the banks of the Ganges. Like the south-east Asian conquest, this epic ''long march'' is also shrouded in mystery. Whether the emperor's objectives in marching an army to the sacred river were political or purely religious is unknown. Certainly, the north of India, though temporarily subdued, was not incorporated into the empire - although holy Ganges water was carried back to a great new capital named in honour of the sacred river, and the ruler who had conquered it.
This capital was called Gangaikondacholapuram - literally ''the City to which the Chola emperor brought the Ganges''. At the centre of their new metropolis, the Cholas built a magnificent temple and a vast three mile-long reservoir symbolically to hold the ''captured'' waters of the Ganges. Both have survived. Under Chola rule, religion and politics grew ever closer together, with the emperor projecting himself as the representative, almost a manifestation, of God on Earth. Large temples were built, for the first time, as royal establishments. The Cholas probably built more temples than any other Indian kingdom or empire. Each temple was a masterpiece. Even today, the Chola heartland - along the Kaveri River in the state of Tamil Nadu - is full of beautiful, delicately carved temples, some the size of tiny chapels, others as big as European cathedrals. In the very centre of what was the empire, there are still 40 Chola temples in an area half the size of greater London. The most spectacular structure is the 63m-high pyramid- shaped centralshrine in the city of Thanjavur, the Chola capital before Gangaikondacholapuram.
Chola art and architecture were among the finest in the world. Indeed, in cast bronze sculpture and hard-stone sculpture, Chola art is unsurpassed. Millions of figures, deftly carved in granite, can still be seen on their temples, while in museums, in Thanjavur and Madras, visitors can marvel at the artistry and craftsmanship of the bronze figurines and statues.
The Cholas not only nurtured an artistic boom; they also fostered a massive expansion in education. Political stability and imperial grants - both to the temples which ran education and to the students themselves - led to the expansion of local schools and elite colleges for higher castes. The education system - which operated from a religious perspective but also promoted literacy, mathematics and astronomy - was probably, at least in part, responsible for the development of a competent imperial administration and broadened international horizons. Some estimates suggest that literacy rose to around 20 per cent - perhaps the highest in the medieval world.
An unplanned result of this high level of education was an increase in intellectual dissidence. One of the greatest Indian religious thinkers - the 11th-century philosopher Ramanuja - was a product of the Chola empire, although he was ultimately expelled for his views. In many ways, he can be seen as the founder of Hindu monotheism with his belief in a unitary personal god, the ultimate font of love and compassion.
In the 12th century there flourished an even more dissident religious movement. The Lingayats professed a sort of cynical humanism which questioned the very fundamentals of religion - the authority of India's holy books, the Vedas (the equivalent of the Bible), and reincarnation itself. Socially, they were also radical, challenging the taboo on widows re-marrying, and condemning child marriages. This dissident movement derived much support from the lower castes.
The empire also increased the importance and institutionalisation of local government. Each group of five to 10 villages had an elected district council, which in turn had endless sub-committees dealing with everything from land rights to irrigation, law and order to food storage. Every household in a district had the right to vote - and the councils enjoyed considerable power. The Chola emperors encouraged their development, probably as a counter-balance to the pow