The Altar of Hieron is a monumental grand altar in the ancient quarter of Neapolis in Syracuse. It was built in the Hellenistic period by King Hiero II and is the largest altar known from antiquity.
The structure is aligned roughly north-north-west to south-east-east, and is located in the Neapolis. Almost nothing except the foundations of the structure survive today. The structure was partly built from masonry blocks and partially carved from the living bedrock. The altar itself is 20.85 metres wide and 196 metres long (exactly one Doric stade). This makes it the largest altar known from the ancient world.
The altar is mentioned by Diodorus Siculus, who attributes its construction to Hiero II. Stylistic analysis of the sculptural fragments from the altar confirms this, showing that they were made at the same time as the third phase of the nearby Greek theatre, which belongs after 235 BC. The votive deposit in the natural grotto under the eastern side of the altar shows that the area was already a sacred site in the Archaic period, not long after the city of Syracuse was established.
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.