It takes a while to figure out what's going on. You see an attendant zip past far too quickly to be on foot and without the bouncing and head wobbling that usually accompanies a full sprint. It's too smooth - she just glides up the pasta aisle, motors through dairy and on towards the alcohol seemingly effortlessly.
From outside the supermarket it's hard to see what's going on, with the bottom half of her hidden by the cash registers. Is there some sort of travelator back there? A slippery surface you can get a run-up towards to then just slide the length of the supermarket?
The reality is only a little more mundane. The attendant, I soon figure out, is wearing in-line skates. They all are. Working in a supermarket the size of three or four produce-laden football fields, I suppose it makes sense. Why walk when you can blade in half the time?
This is the Carrefour supermarket in Calais, France, a major shopping hub for locals and tourists going to and from Britain. Incoming travellers stock up on provisions for the road, while outgoing Brits load up their cars with cheap champagne and beer. You see palletloads of the stuff being wedged into the back of station wagons, parents yelling at each other while children sit glumly in the back.
All the while the attendants glide back and forth on their in-line skates, like Olympic athletes on a food-themed obstacle course. The Carrefour is enormous, a supermarket, hardware store, toy store, electronics store and bottle shop all rolled into one affordable, Briton-filled ball.
To me, it's a fascinating place but then I have a soft spot for the supermarkets of the world, European ones, especially. It might seem dull to some but a visit to a foreign supermarket is a tourist attraction in itself.
Everyone's always looking for a "local" experience when they travel - how much more local can you get than the supermarche? Everyone has to go there and no one will bug you.
Why the European obsession? As a former on-board cook for a Europe-based tour company, Continental supermarkets were my battleground. Have you ever bought three days' worth of food for 35 people? In an hour? In a shop where the labels are all in a foreign language? It was war.
It was also, however, incredibly interesting. I learnt precious little about the real attractions of Europe during that time but I now know a huge amount about the locals' daily shop.
I can't tell you, for instance, which suburb of Rome the Colosseum is in but I can tell you how much a block of parmigiano-reggiano cheese is likely to cost at the Panorama supermarket across the street from Camping Roma. And I can tell you in which aisle to find it.
I'm not sure what year the Charles Bridge in Prague was built but I can tell you the Tesco on the outskirts of the city is one of the few places in Europe that stocks Thai green curry paste. (I can also tell you the Prague Tesco is Europe's spiritual home of the mullet hairstyle; the place seems to be populated by stunning women pushing trolleys for their business-at-the-front, party-at-the-back partners.)
Supermarkets are a cultural education. Their aisles, you find, do nothing to dispel national stereotypes. Italian shops always have an entire aisle dedicated to pasta; German counters are lined with sausages; Hungarian markets stock a lot of paprika; Dutch shelves groan under the weight of mayonnaise.
And the French love cheese. There's a supermarket in Paris - the Metro in Nanterre - that is every fromage lover's dream. It's a wholesalers' shop where caterers and chefs come to keep their enormous pantries stocked. The place is gigantic, like a world made for giants. Mayonnaise comes in 10-kilogram buckets; meat can be bought by the half-cow.
It also has an entire room dedicated to cheese. Not like a little walk-in fridge type of thing but a huge, six-aisle room. Full of cheese. You're given a coat to wear before you step inside, in recognition that it's cold in there and you'll be spending a fair bit of time browsing. There are rows and rows of completely unrecognisable cheeses, some huge and hard, others small, squishy and stinky. There are blocks of roquefort, wheels of camembert and rolls of chevre.
There's an entire country's worth of cheese in that room; it's a dairy-flavoured tour de force that takes you from Normandy to Dijon to the Cote d'Azur. It should be declared a museum, visited by the tourist hordes. Only you can buy the exhibits.
Now that would be a tourist attraction. And you don't even need in-line skates.