Ariel Rios Federal Building

The Ariel Rios Federal Building is eight stories in height and has an unusual footprint that is essentially two semicircles back to back with side wings, resulting in a dramatic sweeping facade. The building is designed in the Classical Revival architectural style. Characteristics of the style found on the building include monumental columns, dentils (square blocks), and balustrades. The exterior is clad in limestone, with granite used to cover the basement level. The rusticated two-story base contains limestone blocks with deeply recessed joints.

The exterior displays columns, porticos, and arcades (arched openings) that are arranged slightly differently on each elevation. The 12th Street elevation is dominated by a colossal portico (entrance porch with columns) and pediment (triangular gable end) that projects from the curved facade and marks the location of the entrance doors. Scrolled Ionic marble columns support a triangular pediment, and similarly designed pilasters (attached columns) are located on the exterior wall. The Pennsylvania Avenue elevation also has a projecting portico that marks the entrance to the Benjamin Franklin Post Office. The pediment is supported by fluted Doric columns that have less ornate capitals than the Ionic columns on the 12th Street elevation. Paneled bronze doors are decorated with molding and floral motifs. The 13th Street elevation is not as varied in detail. It incorporates another dominant portico, and classical motifs on this facade include marble urns, dentils, and acanthus leaves.