It is, quite simply, Russia's most breathtakingly beautiful city.
Walk down Nevsky Prospect, the central boulevard, and you pass over endless canals before eventually arriving at the magnificent Hermitage Museum and the blue Neva river.
Over the bridge is the Kunstkammer. Founded by Peter the Great, this curious museum contains the monarch's celebrated collection of mutants.
But St Petersburg, Russia's second city and former imperial capital, is in danger of being chucked off UNESCO's list of world heritage sites because of plans to build a 400m high skyscraper in its historic center.
Russia's state gas giant Gazprom wants to erect a glass and steel tower nearly as big as the Eiffel Tower just next to the 18th century Smolny Cathedral.
The plan has prompted fierce local opposition. Critics say it will ruin the city's unique low-rise skyline -- and dwarf its neo-classical architecture, which includes baroque villas, flamboyant cathedrals and pleasant Venetian waterways.
On UNESCO Deputy Director General Friday Marcio Barbosa said Russia has until Feb. 1 next year to submit a detailed report on the project's impact, or face penalties.
"If it is like in football, a yellow card," Barbosa told a news conference on a visit to Moscow.
"If the situation does not change we will seriously be considering putting the site on a list of sites that are in danger," he said.
"Being placed on the list is a risk today," he said. Barbosa said the ultimate sanction would be to strip St Petersburg of its world heritage site designation, which it has had since 1990.
He said he hoped it would not come to that. Gazprom, the city administration, and UNESCO authorities are due to meet for talks on Sept. 13.
"The talks will be fundamental in trying to convince them to find alternatives," Barbosa said.
Until last week, the row had been a largely St Petersburg affair.
Conservationists had joined forces with opposition activists to denounce the tower -- dubbing it a symbol of Kremlin arrogance.
They accused St Petersburg's governor of approving the plan to curry favor with Russian President Vladimir Putin, who comes from St Petersburg and is keen to enhance the city's prestige.
Putin has said he will not intervene in the row.
The tower's chief architect, Philip Nikandrov, has insisted that his building won't spoil the city, the result of an extraordinary urban project begun by Peter the Great in 1703.
"The tower fits seamlessly into the city's panorama," he told the St Petersburg Times earlier this year.
Describing it as a "beautiful addition to St Petersburg's landscape," he argued: "Our skyscraper in its present form and shape will beautifully anchor the city's panorama if one is looking from the city center."
So far, building work on the tower in the downtown Malaya Okhta district has not started.
Gazprom Neft, a part of Gazprom, intends to use the vast tower as its new headquarters.
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