A severe drought in Italy has revealed an archaeological treasure in Rome: a bridge reportedly built during emperor Nero's reign that is usually submerged under the waters of the Tiber River.

the remains of the Neroniano Bridge, also known as the Ponte Trionfale or Vatican.

 The remains of the pylons now emerge on both banks. According to Romasegreta, the structure was built by Caligula to connect the Campo Marzio to his Circus located on the left side of the current Vatican basilica. 

But the bridge takes its name from the emperor Nero, who “restructured” it to improve the connections with his properties on the right bank of the river, where there was also the villa of his mother Agrippina. Via Triumphalis was passed over it and reached Veii.

 In 405 AD the emperors Arcadius, Honorius and Theodosius built a triumphal arch in memory of the victory achieved by Stilicone in Pollenza in 402 against the Goths of Alaric, but in the following century the bridge was demolished precisely to prevent the Goths from entering Rome.

https://imperiumromanum.pl/en/discoveries/foundations-of-nero-bridge-in-waters-of-tiber-were-exposed/
https://www.livescience.com/drought-reveals-roman-emperor-nero-bridge

https://news.italy-24.com/local/519468/Drought-the-remains-of-the-ancient-Neronian-Bridge-emerge-from-the-dry-Tiber.html