The wide open spaces of Brazil's futuristic capital were hailed as a sign of the vast, fast-growing country's optimism for the future when it was inaugurated in 1960s.
Now a steel barricade two metres high runs like a scar down Brasilia's central esplanade outside Congress to stop a divided people from coming to blows.
The barrier, which is one kilometre long, will separate rival demonstrators on Sunday when Congress votes whether to impeach leftist leader President Dilma Rousseff on charges of manipulating budget accounts.
For many, it has become a symbol of the deep divisions in Brazilian society and goes against everything the utopian capital, designed by architect Oscar Niemeyer, was built to represent.
"Brasilia was planned as an open space with no division, where you could see as far as the horizon," said Rogerio Rosso, chairman of a committee that recommended the lower house vote to impeach Rousseff. "The fence is bad, but if there are security worries, we have to have it."
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The day before the vote, an uneasy calm hung over the vast esplanade overlooking the sleek, white Congress building and rows of block-like ministries. Hundreds of thousands of protesters are expected on Sunday.
Red banners in support of Rousseff were draped across one side of the wall.
"Congress, the people are watching. There will be no coup," read one, using the term the ruling Workers Party uses to denounce an impeachment it argues has no legal grounding.
Most Brazilians - 61 per cent according to the latest poll - support impeachment, with their country mired in its worst recession since the 1930s and the government embroiled in a corruption scandal centred on state-run oil company Petrobras.
