La Rambla is a promenade that runs down the middle of its own street, with the traffic pushed to the two edges and the plane trees meeting overhead to roof the whole length of it. Flower kiosks, newsstands and portrait painters hold the centre, and wild parakeets screech from the branches where cages of birds once stood. The paving tilts towards the sea, because this was a seasonal streambed before it was anything else.
The torrent ran outside the medieval wall, and the bed only became a promenade when the wall came down in the 1770s. When the convents standing along the line were cleared in the 1830s, their ground passed to the city. That is why an opera house, a covered market and a large arcaded square all sit within a few minutes of each other. It is loudest in the middle of the day, when the crowd moves shoulder to shoulder towards the water, and quietest just after dawn, when the stone is still wet from the cleaning trucks.