New York's High Line goes from train tracks to elevated city park September 28, 2012 -- Updated 2040 GMT (0440 HKT) The park will extend up to 34th Street into the heart of Midtown Manhattan New York's mayor calls the park a local treasure and an international icon The next phase of park construction could cost $90 million (CNN) -- What was once an above-ground freight train line has become a major tourist attraction in Manhattan's popular Meatpacking District. Open to the public since 2009, the High Line elevated park isn't quite complete. A groundbreaking ceremony to mark the start of construction on the third and final section of the park was held last week, hosted by New York Mayor Michael Bloomberg and Friends of the High Line co-founders Joshua David and Robert Hammond. "The park has become a local treasure and an international icon, as well as an important generator of economic growth for our city," said Bloomberg. The heart of Midtown Manhattan The new section of the High Line will be built in three phrases. The first phase, expected to be completed in 2014, will cost an estimated $90 million, financed by a combination of public funds and private donations. It will extend from 30th Street to 34th Street to the west of 11th Avenue and will feature an interim walkway passing over Midtown's Western Rail Yards. The second phase will be built to the east of 10th Avenue, as well as an area where the High Line will pass through Coach's new headquarters building at 30th and 10th avenues. Finally, the third phase will upgrade the interim walkway and the western section of the first phase. Part of the West Side Improvement Project, the High Line opened in 1934 and allowed train traffic to run on tracks elevated 30 feet to put a halt to the years of accidents that had occurred at street level. "An extraordinary" accomplishment Friends of the High Line, which advocates for preservation of the historic structures, was founded in 1999 by David and Hammond in response to a group of property owners who called for its demolition, according to the High Line website. "In the decades to come, long after the final section is open to the public, the High Line will serve as a profound reminder of the extraordinary things we can achieve when the public and private sectors work together for the common good," said Bloomberg.