Compared to, say, the Willis Tower renovations, The 601W Cos.' $500M repositioning of the Old Main Post Office has flown under the proverbial radar. A newly issued permit from the Department of Buildings hints at what the firm hopes to achieve.

The permit allows for the removal and replacement of 2,404 windows at the 2.7M SF building. The cost of the replacement is valued at $12.8M.

The 601W Cos. selected Gensler to reposition the Old Main Post Office, which was vacant for over 20 years and was the subject of several failed redevelopment plans by its previous owner, the late Bill Davies. The plans for the building call for a completely renovated lobby, upgrades to the building's roof, elevators, stairs, plumbing and HVAC, a three-acre rooftop fitness center and a riverwalk, along with 2.5M SF of leasable space. The building is expected to be ready for tenants in 2020. Bear Construction is the general contractor on the redevelopment.