Real estate meets technology giant as Alphabet Inc., parent of Google, takes on development not for the web, but for “smart” cities.

The Wall Street Journal reports that Sidewalk Labs, the company’s division that works with cities to build products addressing big urban problems, “is putting the final touches on a proposal to get into the business of developing giant new districts of housing, offices and retail within existing cities.”

So how would it work, and where would the cities pop up? There’s no clear plan yet, but sources have said that Sidewalk Labs would choose municipalities with large blocks of land that are ripe for redevelopment. These high-tech, high-density metropolises would have higher efficiency infrastructures for water and electricity delivery.

The Verge says the cities would “likely include features such as LinkNYC, the public Wi-Fi hubs that are currently being installed around New York City,” as well as dedicated lanes for self-driving cars.

Among the biggest challenges? WSJ says “it is unclear who would cover the cost of such an endeavor—tens of billions of dollars—since large-scale development typically requires buy-in by third-party investors over a period of years or decades.”