There are only a handful of iconic buildings in most cities, and 100 Federal Street fits that bill in Boston. Clad in a distinctive reddish purple stone, this tower stands out from its neighbors in color alone, yet its most distinguishing feature is the change in plan dimensions – a protrusion for 8 stories, beginning just above street level projects on all 4 sides. The building is comparatively slender both above and below the bulge, which sets this structure in a class of its own.