Since opening, the High Line has become the proverbial example of how cities can transform their underutilized nooks and crannies into vibrant public spaces. Now attracting more than six million visitors a year, the railway-turned-park has inspired a host of similar projects all across the world from Seoul to London. 

Whereas the High Line focused on the reuse of a historic rail line, a new project in Miami, which broke ground earlier this month, is applying the same concept to the space underneath. Designed by James Corner Field Operations, Miami's forthcoming Underline will create a 10-mile linear park beneath the city's Metrorail. 

The project was first inspired when Meg Daly, who came to found the non-profit Friends of the Underline, got into a bicycling accident. Unable to drive, Daly started taking the Miami Metrorail and using the space underneath to find shade during the city's hot summers. Eventually, Daly came to the idea that this underdeveloped, 10-mile stretch had the potential to offer residents a pleasant way out of their cars. 

Miami is one of the most dangerous cities for pedestrians and cyclists; last year, it ranked second in the U.S. for pedestrian fatalities. A through line for the public work, the Underline places changing this at its core. Beyond beautifying the path that already exists with landscaping, dog parks, basketball courts, and other outdoor amenities, the project will also improve intersection crossings to increase safety and help prioritize pedestrians and cyclists in an otherwise car-centric city. 

Having worked with Diller Scofidio + Renfro on Gotham's version, James Corner Field Operations was an easy selection by the city for the masterplan. Though, the design team maintains they entered the project without any preconceived notions, instead working with a coalition of citizens and government agencies to determine what would work best to serve the surrounding communities. 

Still, James Corner and Friends of the Underline have earlier iterations to learn from. Daly's nonprofit is a member of the High Line Network, which helps other cities create similar parks while mitigating the resulting pressures of gentrification on adjacent neighborhoods. What remains needed, Daly told Fast Company, are plans to protect and add more workforce and affordable housing to the area as well as incorporating cafes, markets, and other businesses that can cater to Underline users.

The comprehensive concept is expected to cost around $120 million using a mix of state, county and city funds. The first half-mile for which has already broken ground is scheduled for completion in 18 months.