Mather Tower

The 521-foot (159 m)-high building is sometimes called "The Inverted Spyglass" by Chicagoans due to its highly unusual design, an 18-story octagonal tower atop a more conventional 24-story rectangular "box."

Its design was greatly influenced by the pioneering Chicago Zoning Ordinance of 1923, which placed no limit on the height of new buildings as long as the surface area of the structure's uppermost floor did not exceed 25% of its footprint.

[2] Initial plans called for construction of a second, identical building on North Michigan Avenue, behind the Mather and connected to it by a ground-floor arcade, but onset of the Great Depression in 1929 forced its cancellation.

In 2000 the 4-story "cupola" at the top of the building was demolished because of structural deterioration and safety concerns, after chunks of terra cotta began falling from the facade.

In November 2002, the final phase of the project was initiated when a helicopter lifted the steel framework for a new cupola from a river barge to the top of the tower.

[4] The lower, rectangular portion of the building currently houses the River Hotel, while the octagonal upper stories are occupied by a branch of the Club Quarters chain of membership corporate accommodations.

[12] When considering the need for the restoration of the Mather Tower, it is likely, although not specifically stated, that the falling cladding was a result of cracking terra cotta due to high amounts of strain from the structure itself.