The bike race that began inside an actual supermarket

This year, it also required navigating the checkout area of a sprawling suburban supermarket.

In one of the strangest stunts pro cycling has ever pulled—and cycling fans know that this sport adores a stunt—Stage 6 of the Vuelta on Thursday rolled out from inside a giant air-conditioned Carrefour grocery store on the edge of Jerez de la Frontera, in Andalusia. Riders rolled up an escalator as they arrived and gathered just beyond the cash registers, under bright neon lights.

From there, they tackled roughly 115 miles of Spanish countryside between the dairy aisle and the village of Yunquera.

It wasn’t exactly like having a Super Bowl inside a Costco, but it wasn’t a million miles off, either. The store was closed to the public to prevent any cart-pushing shoppers from bringing down the peloton. But this was not a risk-free zone. The riders set off between a set of barriers that guided them away from the aisles of eggs, produce, and jamón iberico, into part of a shopping mall, and through a tricky chicane until they finally emerged into the Spanish daylight. (To be clear, this section of the race was neutralized for safety—no one was allowed to launch an attack before the bunch had made it outdoors.)

How a major bike race even wound up in a supermarket comes down to a question of sponsorship. Carrefour is one of the Vuelta’s major backers and organizers promised a “unique and original event that will make cycling history."

The thing is, cycling history is already full of absurd detours. Grand Tours—the prestigious three-week races held annually in Italy, France, and Spain—have visited all sorts of unexpected places in recent years, such as Italian motor-racing circuits and Alpine airports perched on mountaintops. Also, the country of Denmark.

Even by those standards, the Vuelta has made a concerted effort to set itself apart. If the Giro d’Italia is for the purists, and the Tour de France is the mass-appeal showstopper, then the Vuelta a España is the collection of kooky and experimental B-sides. It exists for fanatics, completists, and people who don’t have a lot going on in the afternoon in late August.

Before the Vuelta rolled through cathedrals of consumerism, it was rolling through actual cathedrals. In 2021, the race began inside the cathedral in Burgos. And in 2022, the peloton made its way into the Great Church in Breda in the Netherlands, where riders jumped off to light candles and walk their bikes through the nave.

All that gimmickry belies another truth about this race: Vuelta stages can be notoriously brutal. This year’s edition comes with an extra 30,000 feet of climbing compared with the Tour. The late-summer heat is unbearable. And the field usually includes at least a couple of world-class riders out to salvage their seasons after abandoning the Tour. See, for instance, Primoz Roglic, who left France in July after crashing in Stage 12.

He began Thursday’s stage in the leader’s red jersey and sitting next to a boat-shaped supermarket kiddie ride. But by all accounts, the start went smoothly for the entire peloton. The only awkwardness was for the riders on the Lidl-Trek and Intermarché-Wanty teams in enemy territory.

They were sponsored by rival supermarkets.

Write to Joshua Robinson at Joshua.Robinson@wsj.com