This 32-story Back Bay residential tower rises in four segments each of which terminates at a separate roof level, mimicking a spiral staircase as the project is viewed from street level. Employing the up-down construction method, the flat-plate superstructure was able to progress while the foundation work was underway. Integral to the pressure mat and slurry walls, steel columns that would temporarily support the upper levels were built to enable the two phases of concurrent construction.