Macellum of Pozzuoli

Roman origins

The city of Dicaearchia, founded by Greek refugees escaping dictatorship on Samos, was integrated into the Roman Empire as the city of Puteoli in 194 BC. The macellum or food market was built between the late first and early second century AD, and restored during the third century AD under the Severan dynasty.

The building was in the form of an arcaded square courtyard, surrounded by two-storey buildings. Shops lined the marble floored colonnade forming an arcade with 34 grey granite columns. The main entrance and vestibule were positioned on a main axis, which lined up across a tholos in the centre of the square to the exedra for worship which had a portico formed by four large cipollino marble columns. The exedra had three niches for statues of divinities giving protection to the market, including the sculpture of Serapis. The tholos in the centre of the square was a circular building standing on a podium reached by four symmetrically placed access stairways, with sixteen African marble columns supporting a domed vault. Marine animals decorated friezes around the base of the tholos. The courtyard had four secondary entrances on its longer sides, with latrines in the corners of the colonnade and four (probable) tabernae with their own external entrances as well as access from the arcade.

Excavation and influence on geology

King Charles of Naples had excavations carried out between 1750 and 1756, exposing the three large cipollino marble columns which gave the site its name of the "three column vineyard". It attracted visits from antiquarians, among them William Hamilton whose Campi Phlegraei of 1776 showed a distant view of the buildings dry above sea level, and John Soane who "Went to the Temple of Jupiter Serapis" on 1 January 1779 and made rough sketches, as well as a plan of the complex, possibly copied from another drawing.

In 1798, Scipione Breislak described his fieldwork at the site in his Topografia fisica della Campania, and theorised about changes in sea level around that coast. He argued that the evidence did not support the suggestion of falling sea levels worldwide, but thought seismic explanations were inadequate as earthquakes notoriously shook buildings until they collapsed, and the columns were still standing. He concluded that there must have been undetectable movement of the crust of the Earth, but recognised that this was unsatisfactory as the cause could not be seen. In 1802, John Playfair, in his Illustrations of the Huttonian Theory of the Earth, used Breislak's descriptions to support James Hutton's ideas of slow changes, attributing the differing heights of water around the columns to "oscillations" in the level of the land.

Between 1806 and 1818 further excavations exposed the whole of the "Serapeum" or "Temple of Serapis". The excavations lost stratigraphic information in the deposits which had buried the building, but the band of borings or gastrochaenolites left by marine Lithophaga bivalves on the three standing marble columns provided a good record of relative sea level variation.

The antiquarian Andrea di Jorio studied the ruins, and in 1817 published a guidebook to the Phlegraean Fields, with a map of the area which had many hot springs and volcanic craters as well as antiquarian sites including the supposed Temple. By this time the pavement was flooded by the sea, indicating a slight lowering of the land level. In 1820, he published a study of his Ricerche sul Tempio di Serapide, in Puzzuoli, including an illustration based on a drawing by John Izard Middleton showing the three columns with the bands affected by molluscs. …

Modern investigations

More recent investigations of the vertical movements have shown that the site is near the centre of the Campi Flegrei (Phlegraean Fields) caldera and has been subject to repeated "slow earthquakes" or bradyseism of this shallow caldera resulting in relatively slow subsidence over long periods, drowning the ruin, punctuated by periods of relatively rapid uplift that caused it to re-emerge. After a long subsidence through Roman times, there was a period of uplift in the Middle Ages around AD 700 to 800, then after more subsidence the land rose again from around 1500 up to the last eruption in 1538. The land again subsided gradually, then between 1969 and 1973 the land rose by about 1.7 metres (5.6 ft). Over the following decade there was a little subsidence, then between 1982 and 1994 there was uplift of almost 2 metres (6.6 ft). Concerns about risks of earthquake damage and possible eruption led to temporary evacuation of the city of Pozzuoli. Detailed measurements indicated that the caldera deformation formed a nearly circular lens centred near Pozzuoli. Various models have been produced to find mechanisms explaining this pattern.