The dome of a Sun Dome Temple

Jeff recently posted about the Sun Dome of Sartar:

‘With a dome approximately 30 meters in diameter, the Sun Dome Temple stands some 45 meters high, making it larger than the Dome of the Rock in Jerusalem. It is comparable in size to the ziggurat of Ur or Pantheon of Rome.’

Now I’m not an architect or archaeologist, but I like to find how things work, and a dome of that size can only be built in a number of ways. The Dome of the Rock has a wooden frame and roof, covered in gilt, so the Sun Dome of Sartar could be constructed from wood.

In Prax there’s limited access to timber, so what is the Sun Dome there made of?

The Pantheon in Rome is made of Roman concrete, but has a fair bit of bracing, and wouldn’t be the right shape, a possibility, but would probably need dwarven sorcery.

There is a very long tradition of domes in Mesopotamia, dating all the way back to Sumer. The Sumerians could construct arches of fired or dried mud brick and a dome is basically an arch rotated around its central vertical axis. Some reconstructions of ziggurats have a dome atop the shrine at the peak of the ziggurat, but none have survived, and so far as I know, the only pictorial evidence of early domes are in Assyrian reliefs showing small houses.

However, the tradition of domes was carried to Iran and beyond, and there’s evidence of wooden and brick domes. At the Parthian capital at Nyssa (Turkmenistan) there was a hall with thick walls surrounding four columns in the centre probably topped with a wooden dome. During the Sassanid Empire (yes, I know, not Bronze Age), domes were erected on reception halls of palaces such as Sarvestan palace and Ardeshir palace (in Firuzabad). The domes of Sarvestan palace (also known as the Temple of Anahita) date to around 350AD and are the oldest brick domes in the world, the largest having a span of 12.80m, and height of 20m. The dome at the Ardeshir palace is larger with a span of 13.3m.

A 'span' is the length of a structural component that 'spans' between two supports, so the Sun Dome dome in Sartar spans an impressive 30m.

The double layered main dome over the Friday mosque of Qazvin is the biggest Seljuk dome with a span of 15.20m and height of 22m. Built around 807AD it’s well outside any thought of a Bronze Age dome (but Bronze Age in Glorantha doesn’t limit things like architecture or technology), but we don’t know how large the Sumerian domes could be. A surviving arch at the much later Assur has a span of several metres. Could they build larger arches? We don’t know. Where the enormous ziggurats have been rendered into ruined mounds of brick, ancient arches and domes would be long collapsed.

It seems possible that a dome of fired brick would be feasible. Add in some Stasis magic and a dome with a span of 30 metres is possible.