Developer Thornfield and main contractor Laing O'Rourke have reached the highest point of the £350m retail-led The Rock in Bury town centre.
Thornfield said more than 200 companies have worked on the project so far, contributing to an average of 600 people working on-site every day since building began in May 2008.
The average construction spend so far was £1m a week. The Rock is mid-way through its build and is due to open in summer 2010.
The 500,000 sq ft scheme is anchored by Marks & Spencer, a Vue cinema and 24-lane AMF bowling alley alongside other retail and apartments.
Peter Warden, director of Leeds-based Thornfield said: "This is a special day as we thank the workers who have got The Rock to the mid-way point on time, after much hard work and excellent project management.
"Importantly for Bury, a lot of jobs are being created for locals, as well as providing enhanced facilities for the town. In the current economic climate, this is a very important and exciting project for Bury and the North West."
Laing O'Rourke has used 8,500 tonnes of steel and 40,000m3 of concrete to date, during 1m man hours of labour.
Mike Kelly, deputy chief executive at Bury Council, said: "This is a key milestone on the way to transforming Bury town centre and bringing further prosperity to the borough. As an ex construction man, I want pass on hearty congratulations to all the construction companies and their staff for successfully getting to this key point on time."