Millennials may not be quite as devoted to city living as their reputation would suggest. According to a March report from the U.S. Census Bureau, analyzed by the Wall Street Journal, the suburbs are growing markedly faster than cities for the first time since the Great Recession. And a National Association of Home Builders survey in 2015 discovered that 66 percent of first-time millennial homebuyers wanted a house in the suburbs.

Millennials do like the walkability and urban vibe of a city, however, and that's where smart suburbs come into play.

You’ve heard of smart cities, which use technology, including the Internet of Things, to create smarter, more connected public systems. But smart suburbs are smart not in terms of technology (though that may come) but in terms of design and planning.

Adding bike lanes and better public transportation can make existing suburbs smarter, as can turning defunct malls — symbols of yesterday’s suburbia — into mixed-use spaces. But the ultimate smart suburb would start from scratch and revolve around a master plan featuring one or more community hubs where residents can walk, shop, be social and even work.

One master-planned neighborhood is Daybreak, Utah, outside of Salt Lake City. The 4,000-acre community was established in 2004 and is still adding energy-efficient homes and amenities to its four-village layout. Developers situated homes within a five-minute walk or bike ride of a park, the lake, an elementary school, the light rail or shopping so residents could reduce their reliance on cars.

But that's not to say retrofits are out of the question. Carmel, Indiana, just north of Indianapolis, started out as the typical American suburb, but about 20 years ago, Mayor Jim Brainerd reportedly steered the community toward a redevelopment that would see the construction of an amenity-rich central park and pedestrian-friendly sidewalks and infrastructure. Carmel also revamped its historic main street into an "arts and design district" and created a new, larger downtown called the City Center. City planners don't want to completely urbanize the city, though. Instead, their goal is to appeal to a wide variety of residents — those who want to live near a downtown core and those who desire a more traditional suburban feel.

The limited space in some suburbs precludes projects as ambitious as Daybreak, so developers are also thinking on a smaller scale, with mixed-use development projects like The Strand in Allen, Texas. Developer Hines announced in May that it plans to take 135 acres in the Dallas suburb and build the office space, retail space and housing needed to create the "socioeconomic hub" that Allen has been lacking. The developer said the project, which would include public spaces and parks, would also focus on an urban, walkable lifestyle.

As people of all ages migrate back to the suburbs, many want to hold onto the conveniences and social opportunities that cities can provide. As a result, suburbs or communities within them may start to look a bit more like small, walkable, sustainable cities.