Things are beginning to stack up nicely at the site for what might turn out to be the world’s tallest modular-unit residential building. Ironworkers stacked the first few modules yesterday—on Dec. 12.

The eventual 320-ft-tall B2 Bklyn building is the latest far-out adventure of Brooklyn-based developer Forest City Ratner Cos., which is in a partnership with Skanska USA Building Inc. to produce factory-assembled units for modular high-rise residential buildings. Forest City+Skanska Modular is located at the Brooklyn Navy Yard, a few miles from the site for B2 Bklyn at the $4.9-billion Atlantic Yards sports village.

Watching the modules go into their low-level perches was almost a visual letdown. The units, except for one that is a small corner wedge, are shrouded and the perches not very high up. Things should start getting interesting, visually, in January when the erection of the eventual 930 finished units is scheduled to be in full swing. Topping out is expected in early summer.