The Aqua Anio Vetus was an ancient Roman aqueduct, and the second oldest after the Aqua Appia. It was commissioned in 272 BC and funded by treasures seized after the victory against Pyrrhus of Epirus. The aqueduct acquired the nickname of 'old' (vetus) only when the Anio Novus was built almost three centuries later.
Three major restorations were done along with the Appia aqueduct: in 144 BC by the praetor Quintus Marcius Rex during construction of the Aqua Marcia by adding a secondary conduit in the Casal Morena area; in 33 BC when Agrippa took control of the entire water system of the city; and between 11 and 4 BC by Augustus. With this latter, an underground branch was built, theĀ specus Octavianus, which started from the current Pigneto area and followed the Via Casilina and reached the area where the Baths of Caracalla were later built.
Its construction was ambitious as it was four times as long as the Appia and its source much higher. It was clearly an engineering masterpiece, especially considering its early date and complexity of construction.
The Church of St Donatus name refers to Donatus of Zadar, who began construction on this church in the 9th century and ended it on the northeastern part of the Roman forum. It is the largest Pre-Romanesque building in Croatia.
The beginning of the building of the church was placed to the second half of the 8th century, and it is supposed to have been completed in the 9th century. The Zadar bishop and diplomat Donat (8th and 9th centuries) is credited with the building of the church. He led the representations of the Dalmatian cities to Constantinople and Charles the Great, which is why this church bears slight resemblance to Charlemagne's court chapels, especially the one in Aachen, and also to the Basilica of San Vitale in Ravenna. It belongs to the Pre-Romanesque architectural period.
The circular church, formerly domed, is 27 m high and is characterised by simplicity and technical primitivism.