Mayor Rahm Emanuel took part in the event at Illinois and Park Drive in the Streeterville neighborhood.
That's the site of the new Loews Chicago hotel.
Construction actually began in December.
The facility will have 400 guest rooms and more than 300 luxury apartments.
The mayor says Chicago now has more hotel rooms under construction than any other city in the United States.
"We now have more hotels in the city of Chicago than we've ever had, 35,000 and part of that is because the convention and tourism business generates, supports 65,000 jobs in the city of Chicago," Emanuel said.
The hotel is scheduled to open in 2015.
It brings Loews back into the Chicago hotel market.