The protesters came to the heart of Tbilisi to denounce their president, picking their way delicately along paths made perilous by black ice.
By Neil Arun
BBC News, Tbilisi
On open ground by the river, politicians attacked Mikhail Saakashvili, the man who could lead Georgia for another five years if partial results from Saturday's snap presidential election prove accurate.
"Saakashvili wants us to think Georgian history began in 2003," an opposition leader said.
"But you and I know that ours is an ancient country with a glorious past," he shouted, and cheers filled the frozen air.
Facing the demonstrators across the river was the Narikala fortress, established in the 4th Century AD and expanded in the 16th.
Closer to the crowd, overlooking it from a hill, was the glass dome of Mr Saakashvili's new presidential palace, lofty and unfinished.
'Life is still hard'
Mr Saakashvili is a US-educated lawyer who became popular by promising to modernise Georgia.
In 2003, he rode a wave of street protests against his predecessor all the way to the presidency.
Protesters say they will continue to resist Mr Saakashvili
His Rose Revolution offered to transform a poor country in the Caucasus plagued by conflicts and corruption into a confident, prosperous democracy.
He pledged to bring Tbilisi closer to Nato and curb the influence of Moscow, still resented nearly two decades after the demise of the Soviet Union.
Many Georgians who oppose Mr Saakashvili today say they supported him in 2003. Moreover, they agree he has achieved many of his objectives.
But at the polling station on Saturday, they rejected him. At the demonstration on Sunday, the reasons they gave were as varied as the five candidates standing against Mr Saakashvili.
"The courts are corrupt, the prisons are full. There is no justice, no democracy in this country," said Nikusha, a man in his early 20s with his face half-hidden by a scarf.
"He is selling off the country," said another young man, Rati. "Sure, we need foreign investment but he is giving all our wealth away for nothing."
Nearby, a group of women waved posters of the main opposition presidential candidate, Levan Gachechiladze.
"Saakashvili promised us democracy but he has given us a dictatorship," said Nino, in her late 50s.
The opposition has dismissed monitors' reports
Her friend, Ketino, added: "The economy hasn't improved. Life is still hard."
All the protesters in Tbilisi insisted the election had been fraudulent.
They swiftly dismissed the findings of the OSCE, released while the rally was in full swing, that the election had been largely free and fair.
"We have evidence of Saakashvili's supporters carrying away ballot boxes," one young man said. "My friends filmed it on their mobile phones."
International monitors have said they were generally pleased with the election and found no evidence of fraud.
The snap election has its origins in several days of street protests organised by opposition supporters last November.
The demonstrations were at one point the largest seen in Georgia since the Rose Revolution.
Mr Saakashvili eventually ordered troops equipped with tear gas and water cannon to disperse a die-hard group of protesters that had camped outside parliament.
On 7 November, many protesters were hurt in scuffles with security forces and a popular TV channel founded by an opposition leader was forced off the air.
Mr Saakashvili said the country was facing a coup attempt and announced a state of emergency.
As Georgia's foreign allies began criticising the response to the protests, the president announced early elections in January.
His supporters have this weekend been celebrating the results of that election, which they say, affirms Mr Saakashvili's democratic credentials.
The protesters came prepared for the bitter cold
"Saakashvili is far from perfect but he's the best man for this country right now," says Giorgi, who works as a translator for foreign companies.
"These opposition guys think democracy is like a tree-house you build over the weekend. But it takes years of strong leadership for it."
Another supporter of the president takes heart from election results that suggest the opposition to Mr Saakashvili is largely centred on the capital.
"The people of Tbilisi will always take to the streets, whatever the cause. It's in their blood to build barricades," says Natia, a bank worker.
Mr Saakashvili is a former municipal chief of Tbilisi and his most prominent achievements as president have a distinctly civic aspect.
He is widely credited with smashing the crime syndicates that once controlled Georgia and with cutting corruption in the police force.
Some of the president's backers say that while his opponents complain of authoritarianism, it is authority itself that they resent.
This weekend in Tbilisi, the president's authority appeared to encompass even the elements.
On Saturday morning, polls opened after heavy snow had given the city an overnight makeover, brightening all but the drabbest streets.
Meanwhile on Sunday afternoon, no police were needed to disperse protesters already cursing the bitter cold.