Altar of Hieron (Great Altar of Syracuse)
3rd century BCE
m. in length (!!!)
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, slightly to the southeast of the Greek theatre. 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 195.8 metres long (exactly one Doric stade). It sits on a crepidoma with three steps – at base this is 199.07 metres long and 22.51 metres wide. This makes it the largest altar known from the ancient world.
The upper surface of the altar was divided lengthwise into two levels of different heights: the western half was perhaps 6.06 metres high, and the eastern half was significantly taller, rising to a height of perhaps 10.68 metres. There was a cornice and a Doric triglyph frieze running around the top of each level. The whole structure was covered in plaster, which was used to smooth out imperfections in the stone and for the fine decorative details. The overall structure of the altar mimics that of small fire altars which are common votive offerings in Sicily.
There were stairways on the eastern side of the altar at the northern and southern ends, which led up to the lower level of the structure. Each of the staircases had an entranceway which was supported by two telamones. The feet of one of the norther one telamones are still in situ. It is unclear whether it was possible to access the higher level of the structure.
The altar was part of a larger complex. Below the structure, on the eastern side, there was a natural grotto, about 18 metres deep which contained votive offerings, some of which were deposited in the Archaic and Classical periods, long before the altar was built. To the west of the altar there was a rectangular open space with a water-proofed basin in the centre, surrounded by a u-shaped stoa. A propylon on the western side of this compound allowed access to both the open space and thus to the altar itself. In Augustan times, this open space was planted with trees in order to turn it into a sacred grove.