AT FIRST I thought there had been an accident that evening. Several dozen people had gathered under the poplar trees which line Chaoyang Road. It was hard to see what was happening, as Beijing does not waste much electricity on street lighting.
But the hordes of cyclists sailing past without lights, their bicycle frames creaking in the darkness, did not spare them a glance, and it turned out that the crowd consisted of people stretching their limbs in unison and toning up their muscles in the sedate tai chi exercises which are popular throughout China.
Outdoor communal activity on this bustling thoroughfare, with its clothing stalls, pavement barbers fruit vendors and bicycle-menders, is commonplace. During the day, groups of men play Chinese chess on the footpath or a card game called "Hold the Black Ace", and in the warm, mosquito-laden evenings there are always gatherings around the four or five people playing mah-jong with domino-like tiles.
For a westerner who goes close to look, the unselfconscious stares from the people can be slightly intimidating. Even buying produce from a stall can draw a dozen onlookers, curious about the gwei lo, or foreign devil, in their midst.
Once, when I was buying bananas, the vendor, to the amusement of several onlookers including the players in an open-air billiards game, asked me for a high price. "Don't pay it, he's cheating you," cried a young woman, touching off a fierce exchange.
Maybe he was, but street sellers in Beijing often ask the price they think they will get, and they consider foreigners, who are assumed to be rich, as fair game.
The extraordinary thing is that, with the huge numbers of people on the roadways at all times, the level of real crime is so low. There is no mugging and little street theft in Beijing, except of bicycles. Foreigners rarely feel threatened. One hardly ever hears a police siren in Beijing.
However, with this vast country in a state of rapid economic transformation, and a new moneyed class emerging, people are asking whether the streets will stay safe for long.
A neighbour advised us not to go out alone on Chaoyang Road after 10 p.m., and especially to avoid the long, unlit alleys. This is sensible advice in any city but things have got a bit riskier since the construction boom brought in a large transient population of rural workers.
Most of the peasants who work on the construction site next to our apartment block - slight, silent figures who labour day and night - also seem to feel out of place on Chaoyang Road. Some stood watching the tai chi exercises but - like the foreigners - they were not invited to join in.