ANZIO, Italy, Jan. 22— Nero, who was born here and might be considered somewhat biased, liked this town so much that he would come back in the summer, living in a villa that he had built on a sheer cliff overlooking the Tyrrhenian Sea. Caligula was also born here. There are people who wonder how it is that Antium, as it used to be called, managed to produce two Roman emperors of such enduring infamy. In any event, Caligula, too, was known to spend holidays on the Anzio shore. A Flock of Romans

Not much has changed over the millenniums. Romans still flock here when the weather turns warm, to lie on the gritty beaches or to stroll on warm evenings under the palm trees and the pines. They are still Government people, many of them, although hardly in the same class as before. Emperors have yielded to civil servants, and ancient villas, now ruins, have been overtaken by cheek-to-jowl condominiums.


For Anzio, this is the quiet season, a time to catch its breath before the approaching tide of tourism. Pleasure boats lie at anchor, and the gently curving port is calm. There is plenty of life, however. Fishing boats putter in to repair nets and engines, or to sell whatever meager catch the polluted Tyrrhenian has to offer. When Beaches Turned Red

It is also a season for memories, especially this weekend, when the town paused to recall events that turned it from a mere resort into a notable entry in the annals of World War II.

On Jan. 22, 1944, United States and British troops landed on the beaches of Anzio and neighboring Nettuno, taking occupying German forces by surprise and paving the way for the Allied liberation of Rome the following June 4. The landing was deceptively easy. But the Germans swiftly reassembled and counterattacked. Heavy fighting continued into the spring, leaving many thousands of soldiers dead and reducing most of Anzio to rubble.

On a leaden, soggy morning, there were simple wreath-laying ceremonies today at graveyards where the one-time enemies rest.

The United States military cemetery is in Nettuno, where most of the American forces landed. Yet it is the name of Anzio that endures. People in Nettuno say they do not resent that fact, but they are keenly aware of it nonetheless. The Cost: 10,000 Americans

In the cemetery lie 7,862 American soldiers. The walls of a marble memorial bear the names of 3,094 others whose bodies were never found. The British military cemetery, for nearly 2,300 dead, is here in Anzio, where the bulk of British forces came ashore, and there is a field of German dead in Pomezia, 17 miles north.

Italians, especially older ones, come often to Anzio and Nettuno to stroll along the quiet paths that separate the manicured fields of crosses and Stars of David, bright white against the grass. Some leave flowers, especially on Nov. 1, All Saints Day. Mayor Antonio Simeoni of Nettuno says he visits the American cemetery every day, just to get away and think.



''They had a city plan that was interesting,'' said Castore Marigliani, a former Anzio mayor. ''It wasn't accepted because a lot of people would have been deprived of a chance to rebuild houses where they used to be. It's too bad. It was a good opportunity for change.''

Change came anyway. Today's population is more than double what it was right after the war, in part as the result of a surge of migration from the south. Rapid growth put a squeeze on the town, which discovered that relative smallness did not grant it immunity from big-city problems.


For all their problems, Anzio's youngsters do not seem driven by a desire to leave. ''They're curious to see the rest of the world,'' said Mayor Giulio D'Amico. ''But then they come back.''

That is testimony to the pleasantness of life here, some say. Others, though, believe that Anzio could do with a bit of a shake-up.

Mayor D'Amico does not disagree. On his desk, in fact, are plans for a new port, larger than the existing one, providing more berths for private boats and more parking spaces for autos.

Not everyone likes the idea, especially the extra parking spaces, which opponents say will invite too many cars. A few people also detect an element of me-tooism in the plan, part of Anzio's mild rivalry with Nettuno, which just happens to have a spanking-new marina. Wanted: More Tourists

Still others roll their eyes heavenward, and say they have been hearing about a new port for years. Somehow, nothing ever happens, they complain, maybe because of a succession of revolving-door governments at City Hall.

Or maybe, they say, Anzio is a touch too lackadaisical for today's world. That is the opinion of Ugo Mezzabotta, who runs the local Colgate-Palmolive plant, the largest single employer in town, providing work for 850 people.

Mr. Mezzabotta says Anzio should be working harder than it does to lure tourists because they no longer can count on Italian families settling themselves down by the sea for three months at a stretch, as they once did. These days, they stay for two weeks, and move on. Despite this new trend, he says, a lot of people here feel that if it was good enough for Nero, it ought to be good enough for everyone else.

''It is important to build a future,'' Mr. Mezzabotta said, ''and not just live in the past.''

Photo of visitors to the American cemetery in Nettuno, Italy (NYT/Clyde Haberman); map of Italy showing location of Anzio (NYT)