Confirmed: Curia of Pompey, where Julius Caesar was killed, was built in three phases

The site where Julius Caesar was stabbed to death in 44 BCE is known as the Curia of Pompey. It is of interest to many people. A recent paper published in the journal Archaeometry states that researchers from Italy and Spain have confirmed an earlier hypothesis that the structure was constructed in three distinct phases.

The senate in ancient Rome met in a curia. This particular curia was built by the great Roman general Gnaeus Pompeius Magnus. A large theater section contained a temple, a stage, and seating on one end, a large porticus in the middle, and the Curia of Pompey at the opposite end.

The Curia of Pompey was temporarily used by the Roman senators after the Comitium burned down. Publius Clodius Pulcher's followers set it on fire while he was being cremated. When Caesar died at the base of the Curia of Pompey, the replacement meeting site was under construction. The senators who killed him thought assassination was the only way to save the republic.

The Curia of Pompey did not stay open for long. After the assassination, the curia was walled up and may have been set on fire. The site had a latrine built on it. The curia was buried under more recent construction as Rome expanded and wasn't excavated until the 1930s as part of Italian dictator Benito Mussolini's razing of parts of modern Rome to uncover ancient historical sites. The Curia of Pompey was also revealed by those efforts. The remains of the structure can be seen in Rome's Largo di Torre Argentina.

The idea that the curia had been built in phases is not new. The construction of the curia began around 55 BCE using pozzolane rosse from volcanic deposits near the city's center, according to an earlier archaeological study. During the reign of Augustus Caesar, there was a second construction phase using pozzolane rosse.

The National Institute of Geophysics and Volcanology in Rome and their co-authors sought additional confirmation of the hypothesis from the perspective of archaeometry. To determine which quarries supplied the building materials for each phase of construction, they wanted to conduct chemical analysis of the mortar used to build the curia. Two basins are located on the western side of Largo di Torre Argentina, and the third is located on the northern side of Pompey's curia.

Roman concrete was a mix of semi-liquid mortar and aggregate. Portland cement is usually made by heating limestone and clay in a kiln, as well as sandstone, ash, chalk, and iron. The aggregate used to make Roman concrete was made up of fist-sized pieces of stone or bricks.

The Roman architect and engineer Vitruvius wrote about how to build concrete walls for funerary structures that could last a long time without falling into ruins. The walls should be at least two feet thick and made of either square red stone or volcanic rock.

A large number of papers in the last 15 years have shown the exceptional care with which Roman builders produced mortar and concrete. The Markets of Trajan was built between 100 and 120CE and is likely the world's oldest shopping mall. The team analyzed the concrete from the ruins of the sea walls along Italy's Mediterranean coast, which have stood for two millennia despite the harsh marine environment. The secret to that longevity was a special recipe involving a combination of rare crystals and a porous mineral.

Scientists analyzed samples of the ancient concrete used to build the Tomb of Caecilia Metella, a 2,000-year-old mausoleum along the Via Appia. The tephra used in the tomb contained more leucite.