St. Petersburg, Russia (AP) _ This city on the Neva River, once called the Venice of the North, is in critical condition.

Broadcasts of the Goodwill Games show the famed Hermitage Museum, the gilded churches, palaces of the czars and lesser-known royalty, and the canals and bridges that made St. Petersburg famous.

But little is shown of the structural dangers the city is facing.

St. Petersburg was built by Peter the Great in 1703 in order to open a window on Europe. But the swampy, mosquito-ridden wasteland that surrounded the the new Russian capital on an estuary of the Neva River was described by many writers as ''damned.''

During construction, the site was inundated by floods. Superstitious workers believed they were constructing a city against God's will. More than 40,000 bonded laborers died while building St. Petersburg, and it became known as ''the city on bones.''

Virtually all great Russian writers - Pushkin, Dostoyevsky and Tolstoy - wrote about St. Petersburg, a city that bewitched people while poisoning their souls and health.

''A St. Petersburger can be recognized by his pale, unhealthy complexion,'' wrote author Nikolai Gogol. He called it a ''ghost city that emerged from nowhere and will return to nowhere.''

The city may indeed vanish. It could burn, cave in or just die from old age.

Each year, fires destroy some of the city's heritage. A large section of the Library of the Academy of Sciences burned in 1988. Last winter, the House of Writers burned down, as did a 19th century palace.

Museums, libraries and archives - mostly housed in historic buildings - have antiquated fire alarms, or none.

''If our Pushkin House (institute of Russian literature) catches fire, it will burn down in 10 minutes,'' said Academician Dmitry Likhachev. ''The blaze will spread as if in an air tube. Firemen will not even manage to arrive at the scene of the fire in time.''

Alexander Golubkov, an assistant professor at the State Academy of Aerospace, warns that underground passages, many as old as the city itself, threaten gigantic cave-ins.

In an interview with the newspaper Nevskoye Vremya, he said, ''the length of pre-revolutionary underground structures in the city and its environs exceeds the length of all metro lines.''

Golubkov said the first underground passages were built for strategic purposes. Later, Russian noblemen added to them in order to get around without appearing on the street.

Most passages were sealed following the 1905 revolution, but many already had begun caving in - still a danger today.

''Passages under corners of buildings are especially dangerous,'' Golubkov said, citing a three-story house that collapsed last year after a truck hit it.

Passages under the Conservatory have created a facade of giant cracks running from the foundation to the roof.

Golubkov cites other victims of the underground network: A house on the same network that damaged the Conservatory collapsed a year ago. A vacant five-story building that disintegrated after city officials refused to allow a commercial bank to restore it.

Golubkov said the city's famous monument to Catherine the Great could be next. A tunnel passes beneath the monument and there are ominous cracks on the pedestal that spread with each passing year.

Golubkov points to yet another danger. Damage to underground drainage structures that protect foundations from water. ''House foundations and basements are simply rotting away,'' Golubkov said.

Likhachev believes that St. Petersburg began decaying after the 1917 revolution. ''Ever since that time, we only had spent what our ancestors left for us. We destroyed the legacy without creating anything,'' he said.

Many politicians and scientists talk about restoring the city and overhauling the city center. But all projects run against the lack of money and indifference of city authorities.

A 24-hour TV marathon, ''Revival of St. Petersburg,'' was held at the Mariinsky Theater in 1991. ''I was chairman of the telethon, but I don't know where the money went. Probably to pay salaries to officials,'' Likhachev said.

Before the Goodwill Games, hurried cleaning was undertaken throughout the city. New asphalt was slapped on streets. Houses on the main thoroughfare, Nevsky Prospekt, were quickly painted.

''It reminds me of a no-longer young woman who puts a thick layer of makeup on her still-beautiful face, covered with unhealing scratches and ulcers, for her guests,'' said Alexander Kalinov, 25, a lawyer, as he and his wife walked in the ghostly light of the streets of nighttime St. Petersburg.

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