This article is more than 8 years old

This article is more than 8 years old

They call it the Bridge of Knowledge – a spectacular £22m cable-stayed bridge at the entrance to the 2016 Olympic city, not far from Rio's international airport.

Designed by one of Brazil's leading architects and erected by the construction conglomerate Queiroz Galvão, the bridge was inaugurated on the eve of this year's Rio carnival, a monument to the rebirth of the seaside city, which is at the centre of a major economic boom after decades of stagnation.

"Is it a harp, a guitar or a bird?" cooed one local newspaper in an article about Rio's first ever cable-stayed bridge.

It is designed by Alexandre Chan, the architect who was also behind Brasilia's Juscelino Kubitschek bridge. The 780 metre structure links the Federal University to one of Rio's most important motorways, the Red Line, and is a major part of a construction boom intended to improve infrastructure before the 2014 World Cup and the 2016 Olympics.

"What has been done is [to] transform an anti-postcard into a beautiful postcard," said Carlos Minc, Rio's environmental secretary. "Those coming from the … airport will notice the difference."

But while the Bridge of Knowledge is one of the most visible symbols of Rio's economic boom, it has also underlined the city's struggle to escape its past. Drug traffickers who control the Complexo da Mare, a giant slum next to the bridge that tourists pass on their way from the airport to the southern beaches, demanded a $2m (£1.3m) bribe to allow its construction, according to the local press.

One report in the Veja news magazine claimed that three armed men appeared at the site last October, demanding protection money and "donations" to permit work to continue. Queiroz Galvão denied the report, but police reportedly believe the firm had to pay $45,000 a month.

Nearby, another major Brazilian firm, OAS, was reportedly forced to pay to continue work on its $250m expansion of the Yellow Line, another motorway.

One of the firm's engineers was allegedly shot at by drug traffickers after refusing to pay a hefty bribe. The traffickers subsequently upped their demands to $450,000 plus a swimming pool and a football pitch.

Since 2007, Rio's authorities have embarked on a so-called pacification scheme, driving armed gangs from slums including Rocinha and Mangueira, near the Maracana stadium that will host the 2014 World Cup final. But the Complexo da Mare, home to around 130,000 people, is one of many gang-controlled areas in which shootouts remain common.

During a night visit to the sprawling patchwork of slums, the Guardian was introduced to one of the gang leaders accused of demanding bribes from the construction companies.

Flanked by half-a-dozen rifle-toting security guards, the trafficker, a former member of Brazil's armed forces, declined to give an interview on the record, but offered a tour of his drug factory, an anonymous redbrick shack at the heart of the favela. Inside, a dozen young men busily spooned cocaine from glass bowls into small plastic wraps.

The authorities have vowed to pacify dozens more favelas, including the Complexo da Mare, over the coming years. In December, the state security secretary said the slum was next in line for pacification.

Chris Gaffney, a visiting professor at the architecture and urban planning department of Rio's Universidade Federal Fluminense, complained that while the authorities would trumpet the bridge as the city's "newest postcard", they had simultaneously built "noise barriers" around the neighbouring slum, hiding its residents from view.

"This is another showpiece project that creates the appearance of progress, while not addressing the systematic problems it is intended to solve," he said.

• This article was amended on 27 February 2012 because the new bridge is a cable-stayed bridge, rather than a suspension bridge as the original said. This has been corrected.