Calcutta is a city of charming contradictions. The tram company and the Housing Infrastructure Development Corporation also run public bus services, a water treatment plant on the smelly outskirts is named after the city's tallest leader, and the Communist state government which has been struggling to attract industries is sponsoring a film festival on "development and discontent". A "political goon" in the city, according to local newspapers, is called Mandela.

It is a hideously hot and muggy summer, but the air is cleaner after decaying, smoke-belching vehicles were taken off its streets. Calcutta still hosts perhaps the world's noisiest traffic orchestra. Horns of varying sounds and pitches blare round the clock from its cars, buses and auto-rickshaws, creating a sound louder than The Who Live at Leeds.

One afternoon, I travel through the noisy traffic sweating profusely in a rattling Ambassador taxi. I go past hoardings advertising modern dance schools and a blood donation camp in the name of a departed, sun-hatted Communist leader. I pass a dull, whitewashed government building loudly promising "Fish For All" on its walls. I see the streets aflame with posters, flags and bunting hawking parties and candidates' for the city's municipal elections on Sunday. And then I spot an anonymous advert pasted on a wall which simply says, "The time is now!"

Indeed it is. Calcutta - and Bengal state - appears to be on the cusp of historic change. Most people I spoke to said that next year's state elections would see the eclipse of the Communist government, which has ruled uninterruptedly since 1977. The wildly popular and populist Trinamul Congress, a breakaway group from the Congress party, is expected to sweep into the citadels of power at the colonial and sleepy government headquarters of Writers' Building in central Calcutta. And the forthcoming municipal polls will give us some clues as to which way the winds are blowing.

To return to the city's contradictions - did you know that one of its proudest landmarks, the 67-year-old cantilever bridge that spans the Hooghly river is reportedly under threat... from saliva? More than 100,000 vehicles and millions of pedestrians use the bridge every day.

The latter seem to be the culprits. "[The] commuters' collective spit power has reduced the thickness of steel hoods protecting the [bridge's] pillars from six to three millimetres since 2007," a newspaper reports. The tobacco-laced spit, according to a "forensic sciences expert" interviewed by the paper, contains "slaked lime combined with catechu and tannin [that] form an organic compound that acts as a corrosive agent on a steel surface". The Howrah bridge must be the first in the world that is being chewed up by spit.