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Architectural Geology of Rome, Part 1: Eclipsing the Sun for a Moment | Temple of Portunus (various versions from the late 4th-late 1st centuries BC), Latium, Italy

(Updated May 14, 2024)

 

This Ionic-order gem is also known as the Temple of Fortuna Virilis.

 

The Sun is a problematic friend of mine who, like an obnoxious tourist, keeps wandering into my photos. Here, however, he succeeds in giving this lovely and remarkable survivor from Rome's Republican era an appropriately numinous glow.

 

Much more recent photos show that the Temple's stone has been cleared of black crusts and restored to its original colors. However, the outer coating of stucco this building wore in antiquity has not been reapplied.

 

The columns and other portions are made of pitted, off-white Tivoli Travertine, quarried east of the Eternal City in the Acque Albule region. It's an unusual type of limestone that precipitates in hot springs. Geologically very young, it dates just to the Pleistocene and the Holocene, our current epoch.

 

A favorite ornamental facing stone of ancient Roman architects, the Tivoli Travertine is still quarried today. Many examples of its continued architectural use can be found in two great US cities, Chicago and Milwaukee, where it adorns modern skyscrapers and houses of worship. And, of course, it's in evidence everywhere else, too.

 

The cella (inner enclosure) of the Temple is largely made of a more utilitarian rock type, a Pleistocene-aged selection I call the Central Italian Tuff. It was quarried from different lithified-volcanic-ash deposits outside of Rome. One variety found here is the "Peperino dei Colli Albani." As its name implies, it came from the Alban Hills southeast of Rome.

 

Architectural historians often call the Central Italian Tuff "tufa" instead. But despite the confusing similarity of these two names, tufa is actually a much different rock type, of sedimentary rather than igneous origin.

 

Both the Tivoli Travertine and the Central Italian Tuff are products of the intense geothermal and volcanic activity experienced in the greater Rome region in the last 600 ka or so.

 

To see the other photos and descriptions in this series, visit my Architectural Geology of Rome album.

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Uploaded on October 2, 2022
Taken on January 2, 2000