The chalk cellars under Épernay

Under the Avenue de Champagne there is a second town. Something like a hundred kilometres of galleries were cut into the chalk beneath Épernay in the nineteenth century, on several levels, and the biggest houses each hold tens of kilometres of them — Moët & Chandon's alone run to about twenty-eight. They are working cellars: bottles stacked in banks along the walls, chalk arches, rail lines in the floor of the older sections, and a steady temperature of about ten degrees whatever the weather is upstairs.

Photographically it is a completely different register from the street above — warm lamplight against white chalk, long receding tunnels, and no daylight at all. Wide, symmetrical frames down a gallery work best; the light is low enough that a fast lens or a steady support matters more than usual.

Every cellar is private property, entered on a ticketed tour on each house's own timetable. Rules on cameras, tripods and anything that looks commercial are set house by house and are genuinely different from one gate to the next — so ask at the moment you book the tour, and be specific about what you want to do. Turning up and asking at the desk usually gets a no.

Dress for it: ten degrees feels cold after twenty minutes, particularly in August when you arrive in summer clothes. Floors are damp chalk and sometimes uneven, which is worth knowing before someone picks heels for the day.