Above this basement level is an arcaded mezzanine of large round-arch openings in which paired sash windows are topped by a half-round transom.

A dentillated cornice separates this level from a narrower band of three-part windows, above which is a two-level mansard roof pierced by a variety of dormers.

There are projecting pavilions at the ends of the main facade, rising to the top of the mezzanine level on the sides, and the full roof height on the front.

Stylistically the building was described at the time as "German Renaissance"; it is now viewed as transitional between the monumental Second Empire style of Boston's Old City Hall and the Classical Revival.

[2] From 1893 to 1938, the Supreme Judicial Court and the Social Law Library occupied the building, known then as the Suffolk County Courthouse.