Dozens of colonial buildings and beautiful squares in Old Havana have been restored since the U.N. cultural agency UNESCO designated it a world heritage site in 1982. But the rest of the city of 2.2 million people is falling into decay.

"The situation has become critical. There are areas of the city where buildings collapse every few days. The overcrowding is tremendous," said leading Cuban architect Mario Coyula, who fears Havana's architectural beauty is damaged beyond repair.

In teeming, pot-holed Central Havana, poverty coexists with some of the world's finest examples of neo-Baroque and Art Deco architecture built before Fidel Castro came to power in 1959.

It is Cuba's most densely-populated district, with 160,000 people living in 1.3 square miles of crumbling buildings dating from the 1920s and 1930s, many now lacking basic sanitation.

This is the setting for the ribald fiction of Cuban writer Pedro Juan Gutierrez, whose best-selling "Dirty Havana Trilogy," which has been translated into English, recreates an underworld peopled by pimps, prostitutes and black-market hustlers.

Foreign visitors stroll through spectacularly dilapidated streets snapping photographs of the city's rotting grandeur and vintage American cars caught in a bizarre time warp.

Amidst the squalor and rubble, tourists brave darkly-lit streets to climb to the city's best-known private restaurant, La Guarida, perched on the top floor of a palatial town-house built by a sugar baron in 1913.

The building of marble staircases and statues today houses 30 families who built small two-floor apartments inside formerly high-ceilinged rooms, called "barbacoas" because of the way a new floor is inserted like a barbecue grill. A washing line with drying clothes hangs between elegant columns.

In the restaurant upstairs, where a main course costs the same as an average monthly wage in Cuba, photographs on the wall recall celebrity visitors, from Jack Nicholson to the Queen of Spain.

"This building would have collapsed without the restaurant. Its owner has helped a lot with money for repairs," said Enio Ochoa, a former naval engineer living on the second floor.

STANDING BY MIRACLE
Experts say renovating Central Havana would be so costly that demolition is inevitable in many parts. Residents involved in urban planning believe their district can be saved.

"We have an advanced state of deterioration, but renewal is possible," said one official who asked not to be named.
She said 15 percent of the buildings were in very bad shape. "Nobody knows how they are still standing. It's a miracle they have not fallen down," she said.

Iraelio Fernandez's building did collapse. He and his wife moved into an abandoned cinema across the street where he raises chickens and a pig in a roofed space that once housed a 1,000-seat theater called the Palace.

"We moved here until they build new houses," he said.
Cuba's communist authorities say the nation of 11 million has a deficit of 400,000 houses and 43 percent of homes need repairs. Many have not seen a coat of paint in decades.

The government is trying to tackle the problem. In 2006 it injected funds into an accelerated construction program that saw 110,000 units built, almost treble the previous year, but still 40,000 below target.

Architect Coyula said Castro's government, born of a guerrilla revolution that ousted a right-wing dictatorship in 1959, put housing on the back-burner as it gave priority to health and education programs, and industrial development.

The housing crisis worsened when Soviet communism collapsed and sent Cuba into an economic tail-spin in the early 1990s.

Today it is not rare to find three generations of a family sharing the same roof.
Central Havana was the site of the only riots against Castro's rule in the hot summer of 1994 when some 35,000 people took to the sea in rafts is a desperate exodus to the United States.

The Cuban government blames the "blockade" -- as it refers to U.S. sanctions -- for the country's economic shortcomings.

But some Cubans say the government has only itself to blame for the urban decay of Havana.
"It's late to try to save the rich diversity of this architecture," said Cuban writer Antonio Jose Ponte. "It's not far-fetched to think that Central Havana will disappear."