Divide the inside of a dome into coffers that shrink in step with the meridians as they rise, so that their perspective deepens the dome and draws the eye to the light of the lantern.
Rules · Plans · Domes · Columns
The round temple and its hemisphere
Set the columns of a round temple on a circle over a stepped base, carry the entablature round the circle, and cover the cella with a dome whose height is half the diameter of the whole.
dome height ≈ ½ diameter (Vitruvius IV.8, for the peripteral round temple)
Vitruvius describes two kinds of round temple, one with columns only (the monopteros) and one with a cella inside a ring of columns (the peripteral). Renaissance architects read this as the pattern of the perfect building: the circle, having neither beginning nor end, was held to be the figure most fitted to represent God. Bramante’s Tempietto in Rome, built over the supposed site of St Peter’s crucifixion, was the first modern building to realise the type completely: sixteen Doric columns on three steps, a balustrade, a drum and a hemispherical dome.
Serlio (1540) and Palladio (1570) both published the Tempietto beside the temples of antiquity, the only building of their own time to be given that honour.
Related rules
To set a round dome on a square bay, imagine a sphere passing through the four corners of the square; cut it by the four vertical planes of the sides and by the horizontal plane of their crowns. The four spherical triangles left in the corners are the pendentives; the circle at their top carries the dome.
sphere radius R = S⁄√2; arches = sphere ∩ side planes (radius S⁄2); ring at h₀ + S⁄2 with radius S⁄2
If the sphere that forms the pendentives is simply continued above the ring, the bay is covered by a single shallow dome, the sail vault or pendentive dome, which springs directly from the four corners.
crown = h₀ + S⁄√2 (lower than a hemisphere on the ring, h₀ + S)
Lift the dome on a cylindrical or polygonal drum pierced with windows between the ring of the pendentives and the springing of the dome, to light the centre of the church and to make the dome visible from afar.
drum height ≈ ⅓–1 × its radius (Byzantine); much taller in Russian churches
Edge the beds before the portico with box, clip box into figures of animals set facing one another, and in the garden beyond cut it into many shapes, even into the letters of the owner’s name.
Give the villa garden porticoes for sun and for shade, grottoes made in imitation of nature with tufa and shells, evergreens planted in straight rows at equal distances, and hedges of box; set vines on columns over the walks.
Cite this page Chris Paton, “The round temple and its hemisphere”, The Textbook of Architecture, https://textbookofarchitecture.com/rule/round-temple-hemisphere. Text, drawings and models licensed under CC BY-NC 4.0.