If there is one conspicuous difference between the "new China" and the China of a day before yesterday it is the presence of large numbers of tourists. The door has been opened and they are pouring in from every corner of the globe. This ancient city with its legendary beauty, visited by that dauntless Italian traveler Marco Polo in the thirteenth century, is an important tourist goal.

Even in the fierce heat of summer it teems with visitors from the West and with countless overseas Chinese from every part of Asia. An air-conditioned 300-room hotel will be completed next year to accommodate the tourist flood. The estimate in Peking is that 95,000 visitors will come to China this year.

That figure may seen small when compared with the tourist harvest of countries such as Italy, which have earned no small share of their foreign exchange from the tourist traffic. But measured against the barriers that were put up until just recently, it is large indeed.

The gardens are the great attraction in Soochow. They were built for the most part in the Mind dynasty beginning in the 14th century. In their time they were the last word in the luxury of an aristocratic court culture.

"Garden" is an inadequate word. They were pleasure domes created by men of health who chose to retire to Soochow from the hurly-burly of the capital to a life of contemplation, art, music and the dance. The humble administrator's garden is rated one of the four most distinguished in China.

A high official of the Ming dynasty, in traveling about the country on the emperor's business, collected large amounts of gold and silver for favors he could dispense. When he was found out and dismissed, he retired to Soochow, where he commissioned the leading poet of the day to design a garden for him. Eighteen acres in extent, it opens from a modest entrance onto a series of pools filled with lotus flowers, pagodas, the curious rock formations the Chinese made out of concrete, with windows along arcades cut in intricate designs so that the viewer would get a different picture from each window.

One pavilion contained a reception hall with a stage for singing and dancing. The owner's son is said to have lost the entire garden in a single night of gambling.

The central government in Peking has restored several of the gardens: The Master of Nets Garden, The Lingering Garden, The Lion Grove Garden and The West Garden. While the municipality of Soochow pays a large share of the gardens' cost, the gardens are protected as historic monuments by the national trust established by Peking. The centuries took an inevitable toll. Local guides tell the visitor that Chiang Kai-shek's troops stabled their horses in this or that reception hall. The miracle is that so much of the beautiful aura of a long-vanished time has been preserved.

Initially the communist government, which took power in 1949 after the triumph of the civil war led by Mao Tse-tung, was opposed to tourism. They wanted only friendly delegations and representatives of the Third World countries that Peking courts.

So long closed to Americans by the policy of former secretary of state John Foster Dulles, who was determined to isolate China, the stand of the Peking government added to the mystery of a China that has always had a fascination for the West and particularly for Americans.

The change in policy is believed to be related to the hard currency China needs to buy the science and technology essential to modernization.

Most tourists, including the estimated 15,000 from the United States, come for 10 days or two weeks at the most, in carefully guided tours, and Chinese pride dictates that the visitors be given the best they have. Along with this goes unfailing courtesy from high and low. The Chinese have a remarkable tolerance for the invaders who crowd their museums and hotels. Smoke stacks on the outskirts of Soochow mark a rapidly expanding industry. The old and the new are inextricably mingled in present day China.