According to the Daily Camera, earlier this summer, building permits were submitted to the city for a grocery store at the plaza off 28th Street and Iris Avenue.
The store would be about 52,000 square feet in size.
No identifiable information about the occupant of the space was included in the permit. City officials said they have not been provided with a name either.
In a flyer about the rally, Citizens United to Preserve Boulder said "Walmart may be using deceptive practices to build a store in Boulder."
"Boulder's mayor and City Council claim to not know what's happening. Demand that the City Council hold a public hearing to get to the bottom of this," the flyer said.
The rally is planned for 5 p.m. outside the City Council building.
Boulder's mayor, Matt Appelbaum, told the Camera that based off third-party sources, officials believe Walmart plans to move into the space with a grocery store.
"We do have to play by the rules, and the rules are that is a legal-sized store in that shopping center," Appelbaum told the Camera. "It meets all the criteria we laid out for (the commercial center), but we don't pick tenants. We just don't pick tenants."
The newspaper reported some information in the permit -- including certain paint colors and cart corrals -- have some similarities to Walmart's Neighborhood Market store concept.
Neither Walmart, nor the property owner, have commented.