Jubilee 2025 works lead to new surprises in Rome.

Archaeologists unearthed a travertine wall and the foundations of a colonnaded portico, described by the ministry as the "remains of an interesting garden arrangement", overlooking the right bank of the river Tiber.

The find was made during works to pedestrianise Piazza Pia, a €70 million project for the Vatican's Jubilee Year 2025, that will link Castel Sant'Angelo with Via della Conciliazione and St Peter's by channelling traffic through an underpass.

The discovery of a lead water pipe stamped with the name of the owner of the water supply and the garden point to Caligula, Roman emperor from 37 to 41 AD, according to a statement from the culture ministry.

"The inscription reads C(ai) Cæsaris Aug (usti) Germanici: it is therefore Caligula, son of Germanicus and Agrippina the Elder", the ministry said, adding that the link to the emperor also appears to be corroborated by ancient literary sources.

Philo of Alexandria, a Jewish leader, philosopher and scholar in the first century, described how Caligula had received the legation of Alexandrian Jews in the Horti of Agrippina, in a vast garden overlooking the Tiber, separated from the river by a monumental portico.

The ministry said that excavations in Piazza Pia at the start of the last century unearthed other lead pipes "inscribed with the name of Iulia Augusta, presumably Livia Drusilla", the second wife of Augustus and grandmother of Germanicus.

"It is probable, therefore, that this luxurious residence was inherited first by Germanicus and then, upon his death, to his wife Agrippina the Elder and then to her emperor son", the ministry stated.

The latest discovery in Piazza Pia came during works to relocate the newly-unearthed remains of a fullonica - the ancient Roman equivalent of a dry cleaners - which will eventually be displayed in the nearby grounds of Castel Sant'Angelo.

Last month Rome's mayor Roberto Gualtieri insisted that the discovery of the fullonica would not slow down the Jubilee project, one of the biggest currently underway in the Italian capital, and that its December 2024 completion date still stood.

Photos Fabio Caricchia - Soprintendenza Speciale di Roma