Short answers, pulled from the story.
The onion dome is a bulbous roof structure that tapers to a point and swells wider than its base, with origins tracing back to Syria during the 7th century Umayyad Caliphate era. Historical evidence shows early bulbous domes depicted in 7th-century Syrian mosaics and a prototype appearing in Chehel Dokhter, Iran, by the mid-11th century.
The onion dome gained popularity in Russia as early as the 13th century and reached a peak during the 17th and 18th centuries before the Petrine period. It was used to prevent snow from accumulating and collapsing the roof due to its steep curves, serving a critical function in the harsh Russian climate.
Scholars including Boris Rybakov, Nikolay Voronin, and Sergey Zagraevsky debated whether the style was imported from the Orient or evolved independently within Russia. Rybakov analyzed chronicles in 1946 to argue for indigenous origins, while Zagraevsky surveyed 11th-century icons to conclude that onion domes appeared in pictures from the 12th century.
The onion dome has become popularly believed to symbolize burning candles, a theory argued by religious philosopher Prince Evgenii Troubetzkoy in 1917. Another explanation posits that the shape was originally regarded as a form reminiscent of the aedicula in the Church of the Holy Sepulchre in Jerusalem, dating back to 12th-century construction by the Crusaders.
The onion dome appears in Western and Central Europe, the Middle East, and the Americas, including Baroque domes in the Holy Roman Empire built by Johannes Holl in 1576. It is also common in Catholic churches across southern Germany, Switzerland, and Austria, as well as in Mughal architecture, Sikh Gurudwaras, and the Baiturrahman Grand Mosque in Indonesia.