Domes do not have to be perfectly spherical in cross-section, however; a section through a dome may be an ellipse. If the baseline is taken parallel to the shorter of an ellipse's two diameters, a tall dome results, giving a sense of upward reach. A section across the longer axis results in a low dome, capping the volume instead. A very low dome is classified as a saucer dome. All the surfaces of any dome are curved. A spectacular innovation, one that is at the heart of Baroque style, is the oval dome, which gives axial direction and movement to the space beneath it. Though the oval dome is typically identified with churches of Bernini and Borromini, the first oval dome was erected by Vignola for a small chapel, Sant'Andrea in Via Flaminia often called Sant'Andrea del Vignola. Julius III commissioned the dome in 1552 and construction finished the following year. The largest oval dome was built in the basilica of Vicoforte by Francesco Gallo.
Domes that have been disproportionately influential in later architecture are those of the Great Stupa in Sanchi (actually, a solid mound with stone facing), the Pantheon in Rome, Hagia Sophia in Istanbul (or in that time Constantinople), and the Dome of the Rock in Jerusalem. In Western architecture, the most influential domes built since the Renaissance have been those of St. Peter's Basilica in Rome and Jules Hardouin-Mansart's dome at Les Invalides in Paris. The dome of St. Paul's Cathedral in London was the inspiration for the United States Capitol in Washington, which in turn inspired domes of most of the US state capitols.
A cathedral is often referred to as a duomo in Italian or "dom" in German. This is not because so many are crowned with crossing domes over the space where transepts intersect the nave, but instead stemming from the Latin noun "domus", house, or in this case the "domus dei", the house of God. A dome is a mark of palatial ambitions whenever it is seen crowning a residence. The first residential domes were seen in Nero's Domus Aurea that covered the slope of the Palatine Hill, built after the Great Fire of Rome of AD 64 with a lavishness that scandalized the senatorial class.
In the 20th century, thin "eggshell" domes of pre-stressed concrete by architect-engineers such as Nervi opened new directions in fluid vaulted spaces enclosed beneath freeform domed space which now might be supported merely at points rather than in the traditional constricting ring.
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