By Mike Dougherty

PHILADELPHIA (CBS) — It was a milestone on Wednesday in the construction of building in Center City. It’s the latest development in the revitalization of East Market Street.

Iron workers perched 17 stories above ground placed the final steel on The Ludlow at 12th and Market Streets. The “topping off” marks the completion of one phase of the $200-million project.

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“It’s really celebrating the iron workers who have spent the last six months of putting this structure together,” said Daniel Killinger with National Real Estate Development.

Killinger has been waiting for this day.

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“A lot of us have worked for many years on this project,” he said, “and we’re excited to have this milestone today.”

He says he can’t wait to see the finished product.

The building will be mixed use with 322 residential units and more than 130,000 square feet of parking and retail space.

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Construction is expected to be completed in Spring 2017.