[2] It has a unique construction style featuring exterior load-bearing walls and an interior steel frame, providing a transition between accepted and new building techniques.

By mixing modern building techniques, such as metal framing, fireproofing, elevators and plate glass, together with traditional ones, such as brick facades and elaborate ornamentation, Burnham and Root sought to create a bold architectural statement.

As the master artisan, Root drew upon a variety of influences in designing the interior and exterior spaces, including Moorish, Byzantine, Venetian and Romanesque motifs.

Of particular note was a "floating" foundation—a reinforced concrete slab that provided the building's weight with a solid platform atop Chicago's notoriously swampy soil.

"There is nothing bolder, more original, or more inspiring in modern civic architecture than its glass-covered court", wrote Eastern critic Henry Van Brunt.

[10] Wright's work on the Rookery recast the entryway in his Prairie style and added a sense of modernity through his simple but effective lighting design.

The marble and decorative details added a sense of luxury to the lobby's steel-laden interior, marked by Burnham and Root's skeletal metal ribbing.

[10] The red marble and granite, terra cotta and brick façade of the building is a combination of Roman Revival and Queen Anne styles that embraced Richardsonian Romanesque architecture.

In keeping with contemporary tastes, Wright's design covered Root's elaborate wrought iron finishes with white carved Carrara marble surfaces.

[2] The second renovation, completed August 24, 1931, by former Wright assistant William Drummond, modernized many of the interior elements, including new elevators, and brought period touches to the building, such as Art Deco detailing.

[10] The third renovation, in 1992 by Daprato Rigali Studios, brought the building back to much of its original splendor, reopening the light court ceiling after it had been covered over to protect against leaks.

[13] In 2011, Office for Visual Interaction completed the lighting design for the facade, illuminating the architectural features of the building with state-of-the-art LED technology.

The building was purchased in October 2007 for $73 million by an investment group controlled by a European family, and advised by Zeb Bradford of Metzler North America Corp.