Atlanta is transforming a 22-mile ring of former railroad tracks into a multi-use transit corridor and public space.

The old rail corridor -- which is anywhere from 44 to 200 feet wide -- will have paths for bicyclists, pedestrians and a new track for a modern street car. Adjacent to the line will be parks, affordable housing, restaurants, shops and other attractions. The ring will intersect Atlanta's existing public transit system at several points, and ultimately connect 45 neighborhoods.

Construction started in 2008, and over $350 million has already been spent to complete several miles of trail. It's projected to be finished in 2030, with a final price tag of $4.4 billion.

The entire project was the brainchild of Ryan Gravel, a then-graduate student at Georgia Institute of Technology.