About half of Via Fondazza’s residents belong to the Facebook group. Those who do not use the Internet are invited to events via leaflets or word of mouth.

“I’ve noticed that people at first wonder whether they need to pay something” for the help from others, said Mr. Bastiani, referring to the experience of an 80-year-old woman who needed someone to go pick up some groceries for her, or a resident who sought help assembling a piece of Ikea furniture.

“But that’s not the point,” he added. “The best part of this is that it breaks all the schemes. We live near one another, and we help each other. That’s it.”

The impact of the experiment has surprised almost everyone here.

It “has changed the walking in Via Fondazza,” said Francesca D’Alonzo, a 27-year-old law graduate who joined the group in 2013.

“We greet each other, we speak, we ask about our lives, we feel we belong here now,” she said.

The exchanges usually start virtually but soon become concrete, allowing residents to get to know one another in person.

Everyone on Via Fondazza seems to have an anecdote. Ms. D’Alonzo remembers the party she gave on New Year’s Eve in 2013, when her then mostly unknown neighbors brought so much food and wine that she did not know where to put it.