What is the diameter of the dome of Cincinnati Union Terminal?

The dome of Cincinnati Union Terminal is 180 feet in diameter, or about 55 meters across.

The terminal’s celebrated Rotunda is topped by a huge semi-dome measuring 180 feet wide and 106 feet high. Its scale made it an extraordinary engineering achievement when the station opened in 1933, and it was described as the largest unsupported half-dome of its time.

Cincinnati Union Terminal was designed as a monumental Art Deco railway complex by the architectural team of Fellheimer and Wagner, with Paul Philippe Cret serving as consulting architect. The Rotunda was intended to make rail travel feel modern and civic rather than merely functional. Its interior includes colorful mosaic murals by Winold Reiss and extensive marble finishes.

A frequent mix-up is calling the structure a full dome. Architecturally, the Rotunda’s roof is a semi-dome: the curved half of a dome attached to the terminal’s front wall. The 180-foot measurement refers to its width or diameter across the curved span, not its height; the vertical rise is 106 feet.