New York's elevated urban park was originally a freight railway line.

Originally built in 1934, the idea was to take freight trains off the busy streets of Manhattan's West Side while still providing transport services to the area's many factories and warehouses. Parts of the line ran directly through buildings to make it easier to load and unload from the area's meatpacking plants.

The train line closed in 1980 as manufacturing left Manhattan and trucking became more economical. The elevated line was unused for years, and the city was going to tear it down.

In 1999, a group of area residents organized to save the structure and turn it into a park. The first section opened in 2006 to rave reviews. Locals and tourists alike appreciate the boardwalk, benches, native plantings and not-quite-birds-eye view the park affords.

The third and final stage opened earlier this year, and over 4 million people now visit the park annually.

Related: How New York is preparing for the next superstorm