IN THE VALLEY OF DRY STONES

WITH no sign, no fence, and no protection of any sort, Kot Diji appears from even a few yards away to be just one more pile of rubble. Probably of more interest to tourists, the 19th-century fort bearing the same name, on a hill literally across the road, has been largely restored.

Yet finds among the broken pottery of Kot Diji (about 350 miles north of Karachi, in Pakistan's Sind Province) show that it dates back nearly 5,000 years - to 2,800 BC - predating by about 300 years the better-known Harappa and Moenjodaro archaeological sites in the same region.

These remains provide the major sources of information about the early Indus Valley civilization, also known as the Harappan culture, which ranks with early civilizations of Egypt, Mesopotamia, and the Huang Ho Valley in China.

The much better preserved site at Moenjodaro (see map) was partly excavated by the British in 1922. A highly developed city of 50,000, with wide streets, two-story dwellings, large civic and religious structures, and even an extensive brick-lined sewage system, was uncovered.

A small but well-maintained museum of artifacts on the site at Moenjodaro includes personal seals, the original signatures, bearing the image of an animal or human form, and sparse examples of so far untranslated writings.

Without decipherable writings, knowledge of this Bronze Age people is limited to deductions about the obviously well-planned cities and their utensils.

All told, about 240 acres have been uncovered, roughly 25 percent of the total. At its height, the Indus Valley civilization included 400 cities and towns in what is now Pakistan and India.

But the sites are threatened by rising ground water and sporadic flooding. No excavation has been done since 1962, as efforts have turned to reducing the salinity of the soil, which can damage the bricks and foundations.

Irrigation of surrounding areas had raised the water table, pushing earth salts upward. According to the Pakistani Archaeological Department, 27 wells have now lowered the water table to 30 feet. The United Nations Educational, Scientific, and Cultural Organization (UNESCO) is providing technical assistance and substantial financial support in an effort to save this ancient treasure.