India's extraordinary history is intimately tied to its geography. A meeting ground between the East and the West, it has always been an invader's paradise, while at the same time its natural isolation and magnetic religions allowed it to adapt to and absorb many of the peoples who penetrated its mountain passes. No matter how many Persians, Greeks, Chinese nomads, Arabs, Portuguese, British and other raiders had their way with the land, local Hindu kingdoms invariably survived their depredations, living out their own sagas of conquest and collapse. All the while, these local dynasties built upon the roots of a culture well established since the time of the first invaders, the Aryans. In short, India has always been simply too big, too complicated, and too culturally subtle to let any one empire dominate it for long. True to the haphazard ambiance of the country, the discovery of India's most ancient civilization literally happened by accident. British engineers in the mid-1800's, busy constructing a railway line between Karachi and Punjab, found ancient, kiln-baked bricks along the path of the track. This discovery was treated at the time as little more than a curiosity, but archaeologists later revisited the site in the 1920's and determined that the bricks were over 5000 years old. Soon afterward, two important cities were discovered: Harappa on the Ravi river, and Mohenjodaro on the Indus .ars, occasionally fighting (and often losing to) invaders from the north and China, who seemed to come and go like the monsoons. Unlike the Greeks, the Romans never made it to India, preferring to expand west instead.