New York City officials have officially kicked off a new 5 million-square-foot development project that will be built on a platform over railroad tracks in Manhattan.

The Manhattan West project west of Penn Station will include two office towers and a residential building.

The $4.5 billion project will require a 120,000-square-foot platform over the tracks that lead to the train station.

Mayor Michael Bloomberg joined officials from developer Brookfield Office Properties on Tuesday to announce that construction has begun.

Brookfield Office Properties CEO Dennis Friedrich said the project will serve as a much-needed expansion of Manhattan’s central business district. He said the buildings will open in 2016.

Bloomberg said the development will create jobs the city needs.

(AP)