Hadrian's Library was created by Roman Emperor Hadrian in AD 132 on the north side of the Acropolis of Athens.
The building followed a typical Roman Forum architectural style, having only one entrance with a propylon of Corinthian order, a high surrounding wall with protruding niches (oikoi, exedrae) at its long sides, an inner courtyard surrounded by columns and a decorative oblong pool in the middle.The library was on the eastern side where rolls of papyrus 'books' were kept. Adjoining halls were used as reading rooms, and the corners served as lecture halls.
The library was seriously damaged by the Herulian invasion of 267 and repaired by the prefect Herculius in AD 407-412. During Byzantine times, three churches were built at the site, the remains of which are preserved: a tetraconch (5th century AD), a three-aisled basilica (7th century) and a simple cathedral (12th century), which was the first cathedral of the city.
References: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.