Ah! Tourists! But will they love Greece to ruins?

Villagers in Olympia, site of the ancient Olympic ruins, always looked forward to September, a time for revelry, peasant markets, fireworks, and occasional wild abandon. Their three-day festival was a 2,500-year-old mythical Greeek god who represented joy and uncontrolled behavior.

A few years ago, Olympia officials put a stop to the harvest celebration. "It was too Oriental," says the mayor, "and it gave a bad image to tourists."

Since the 1950s, tourism in Olympia has steadily climbed, reaching half a million visitors a year. Souvenir shops line the main street, four discos have opened, and the population has almost doubled in 10 years.

Tourists are a welcome sight to many Greek villagers, but in private a number of top government officials are beginning to wonder if Greece is not detroying the very thing it is selling. Zorba the Greek may just be running a fast-food restaurant these days.

?Tourism is sapping the heart out of Greek culture," a leading banker says. "We take an island of 1,000 Greeks who have been living there for 2,000 years and thrust 3,000 pot-smoking backpapers at them."

In certain areas, the government has said "enough is enough" and all but stopped supporting investments in new hotels or other tourist facilities. These include the Athens and Thessaloniki areas, northern Rhodos, Mykonos, Patras, estern Corfu, Iraklion, western Mycenae, and northern Kos.

"Tourism needs more guidance," says Yannis Costopoulou, managing director of the Credit Bank. He suggests that the islands of Corfu and Rhodos, already packed with European tourists, be given tax-free status for business, tourist facilities, and retirement homes. "That would help keep other Greek villages safe from tourism," he says.

Some resort isles, such as Samos, are just starting to be developed. "These islands are being destroyed," says Constantine Coulombis, owner of a tour company catering to Americans. "Twenty years ago you would think you were in paradise. Now the islands are being covered with hotels." On Mykonos, for instance, which has become a haven for European jet-setters and homosexuals, the government-run hotel stands cheek by jowl with an old, quaint windmill.

On the island of Skiathos, which offers 60 beaches, fishermen who use to sell fish straight from their boats now display signs offering trips to "Banana Beach ," noted for its nude sunbathing. The 3,500 villagers have opened 2,500 rooms in their own houses in addition to the hotels. At about $10 a day per room, they earn enough to idle away the winter, perhaps adding another room to make even more money. Piles of trash are common, and in the morning, tourists in sleeping bags can be found scattered about the parks.

"The culture deteriorates," a top government official admits. "Farmers have become tourist aides or disco operators. And drug use is increasing among Greeks. We need better government watchdogs. But we just don't have the trained people."

Tourism does not change morality or tradition, countercharges Prof. George Daskalakis, president of the National Tourist Organization of Greece. "There is some change in everyday behavior: The tourists wear shorts, and now some Greeks wear too cosmopolitan, rather than keeping our Greek culture."

But, retorts Dr. Daskalakis, "Did Greenwich Village change the United States?"

The ups and downs of the tourist market also give pause to officials, even though the industry ranks with shipping and emigrant remittances as a top earner of foreign exchange ($1.7 billion estimated this year).

The government, which expected investment in tourism to expand 17 percent a year, has seen a disappointing 4 percent or less investment pace the last few years. A survey of about 70 Greek tourist companies by ICAP Hellas, which tracks industry trends, shows about 40 percent with losses during one or more of the past three years, with level over half the Greek hotels running on red ink.

In 1981, the number of visitors is expected to rise 6.1 percent, about half the rate during the 1970s. Last year, the number of tourists decreased 9 percent.

Still, the number of tourists has more than doubled, to about 5.3 million visitors a year from fewer than 2 million at the end of the military junta in 1974.

British and German tourists dominate the trade, and their numbers will likely increase as Greece's membership in the Common Market brings in European investment in tourist facilities. The Common Market will also subsidize rural development, such as roads, which will even out the highly concentrated tourist flow.

Despite the problems, a survey of European tourist prices by the Italian-based Institute of Special Statistics in Florence found Greece the cheapest place for visitors, with Portugal, Italy, and Spain close behind. Britain was the most expensive. In 1982, however, the government has lifted hotel price controls, leaving only a minimum charge. This may substantially raise prices, and also allow tourists to bargain for cheaper rates.