What makes Brunelleshi's dome of the Florentine Cathedral so?
There is a great book on the subject, Brunelleschis Dome: How a Renaissance Genius Reinvented Architecture by Ross King. It is in my opinion a well-written more or less biographical sketch of his life and has the dome as a focal point of his life and development of the dome. He was the winner of a competition to build the dome. Apparently, the very anxious church and city fathers wanted to build the greatest cathedral in Italy and started building without having a solution for the dome, thus the competition. Brunelleschi was mechanically intuitive and apprenticed as a clockmaker. He developed skills as an artist and did bronze sculptures and doors that are still revered as some of the greatest. His architectural skills were self-taught, intuitive and made the huge dome possible by an innovative technique of building in ever-decreasing concentric circles and an innovative combination of scaffolding and cranes. See the book for detail. While working on the dome which took years, he also had to deal with personality conflicts with other great artists and architects of the time as well as financial and personal disasters and local wars. The dome remains one of the largest ever constructed and certainly one of the most beautiful. Ive had the opportunity to visit the cathedral several times and have always found it awesome. If you are really interested in the man and the dome, please read the book, it was very insightful into his art and engineering accomplishments as well as the turbulent social climate he worked in.