Federal Reserve Building refurbishing

This was a cool old building maybe 4 stories high, with a fancy stone exterior across the street from my workplace. They removed the marble, gutted the works, left the exterior walls held up by skeletal bracing and built a modern steel framework inside. Now they're working on a glass tower above the original ( you can see my building reflected in the glass).
The plan seems to be to put the marble back eventually so from the ground it'll still seem cool. Meanwhile some workers are hanging out in a window finishing something or just taking a break.