The Temple of Serapis sits not far from the sea in the ancient town of Pozzuoli. If you find yourself strolling along the waterfront, you will certainly happen upon it. Though it is not a temple at all, as its name would suggest, it is an important symbol of the region’s Roman roots, and more importantly, of the geologic forces at play in the Campi Flegrei,

The Temple of Serapis was first excavated in the mid 18th century, around the same time gentlemen archaeologists were unearthing Herculaneum and Pompeii. Known simply as “the vineyard of the three columns” then, upon finding a large statue of the God Serapide, archaeologists believed they had found a serapeum, a temple dedicated to the god of Serapis.

The god of the underworld, as well as the god of the sun, healing, and fertility, Ptolemy I of Egypt created Serapis as an Egyptian-Greek god to unite the two cultures. The statue of Serapis was eventually placed in the National Archaeological Museum, and it wasn’t until the early 20th century that archaeologists learned that the site was a macellum, the Roman marketplace of Pozzuoli first built in the late 1st century AD.

As you near the macellum, the first thing you will notice is that it lies about 30 feet below sea level. The second, is that its ancient granite columns seem to be suspended atop a mirky pool of water, leaving you with the impression that they are either rising up from or descending into the sea. Thanks to a geological phenomenon known as bradyseism, that is exactly what’s happening.

Originally attributed to changes in sea level, geologists later learned that the ground was moving slowly up and down with the ebb and flow of magma chambers deep within the earth. From the Greek bradus = slow and sism = movement, bradyseism is prevalent throughout the Campi Flegrei and the macellum is perhaps the most important example of it in the world. In fact, scientists have been documenting the ruins’ movements since the 18th century, when they found evidence of molluscs on several columns indicating that the columns were at one time submerged to a depth of at least 7 meters.