The main architect of the entire church was Arnolfo Di Cambio, who mastered the nave and the aisles. It was Brunelleschi, though, who pioneered the dome, which is the largest of its kind and was considered an architectural wonder of its time. He was a mathematical genius, and the dome reflected his prowess. Serving under him was the apprentice Leonardo da Vinci, who was young at the time and would go on to pioneer a number of Renaissance buildings. 

This church is Basilican, which is noteworthy for its cross-style plan, where the long nave is flanked by an aisle on either side. It is longer than it is wide, like a cross would be. The church cannot be a hall plan, as it has aisles and is not oriented in a single rectangular plan. The same is true with octagonal; the church plan does not follow the format of an eight-sided church. Cruciform churches were not popular until much later than this point. 

The church at the time had more money than the state and the wealthiest families of Italy. Likely it was the Catholic church itself that commissioned the cathedral. Given also the time it took to build, kings had come and gone and the Medici had gain and subsequently lost their prominence in Italian society, but the church was omnipresent and dominating for the three hundred years it took to go from construction to completion. 

The dome is Renaissance; it was built two hundred years after the facade of the cathedral, under the guidance of Brunelleschi and his pupil, Leonardo da Vinci. both were pioneers of the Renaissance movement. Note also the shape and nature of the dome; it is very much in the tradition of Classical Greek and later Roman temple construction styles. It is meant very much to emulate the grandeur of the Parthanon, much like the rest of the Renaissance movement emulates Roman and Greek wonders. 

A key feature of Gothic churches is their height. The supports on the sides were added to prevent structural problems. Known as "flying butresses", these supports were transformed from simple structural elements into elaborate ornamentation.

"Gothic" architecture describes the dominant forms in Western European architecture from about the twelfth century to the sixteenth century. Gothic cathedrals are monumental in scale and scope, structured around buildings that are cross-shaped when viewed from above, and feature lots of ornamentation and design elements, including vaulted arches, statuary, rose windows, flying buttresses, and grand columns.

Flying buttresses are ornate supports that stick outside the walls of Gothic church architecture, particularly cathedrals. Buttresses were necessary to keep the new, massive stone cathedrals of the middle ages standing. While they were originally functional, church builders made them reflect and enhance the design of their buildings.

The Flamboyant (or Late) period of Gothic architecture contains a combination of tracery and ogee arches. "Flamboyant," from the French word for flaming, denotes its highly decorative style.

Gothic architecture, particularly in the building of churches and cathedrals, featured a number of ornate features. One of the most peculiar was the use of gargoyles, small stone figures of grotesque characters that were placed on the sides of buildings. These figures would often be placed between sculptures of saints and kings, and were viewed as protective features. Some gargoyles also functioned as drainage pipes (through holes in their mouths).

The depressed arch was much different from the other arches found in Gothic architecture. It was designed to look as though it had been flattened by a great pressure, and was very wide. There is no such thing as an Italian arch.