This fall, one of the world's biggest private developments will start going up on the site where New York City once hoped to host the 2012 Olympics.

Hudson Yards on Manhattan's West Side might have become a stadium if the city had won the summer games. Instead, a $15 billion small city within a city will fill 26 acres of land by the Hudson River.

Developer Stephen Ross tells The Associated Press that groundbreaking is planned sometime in October on the first of a cluster of skyscrapers. They'll be surrounded by public parkland, a cultural center, restaurants, shops, a hotel and a school.

Hudson Yards was one of many venues NYC proposed to use if it  hosted the 2012 Olympics. Take a look at how some of the other sites would have looked.

One of the towers is being designed by architect David Childs, who planned One World Trade Center, the city's highest building still under construction.