Inside, the spectacle has no equal: the nave is an enormous empty space that widens with the slow succession of its massive pillars. The dimensions are astounding: the height alone at the top of the dome is 90 meters, as high as a thirty-storey building.
The gigantic size of the construction is the cause of an infinite series of structural problems: the weight of the vaults made it necessary to add flying buttresses along the sides that, not pleasing to the Florentines, had to then be hidden behind extensions rising from the external walls.
With Talenti's death, the building had only just begun: the naves were finished at the end of the 1300s and the three chapels of the apse would have to wait until the beginning of the next century.
In the meantime, the solution still remained to be found for the biggest problem of all: construction of the enormous dome. 125 years would pass from the beginning of the works and, of course, the addition of Brunelleschi's genius, before Florence could be adorned by its unmistakeable outline. It was built in sixteen years and still today is the largest masonry-built dome anywhere.
The church reveals a mix of civic and religious meanings: the cathedral's decorations as a whole aim at celebrating the spiritual greatness and dignity of the human being.
In the side naves, mans' civic virtues find sober expression in two famous frescoes, the equestrian portraits of John Hawkwood by Paolo Uccello, and of Niccolò da Tolentino by Andrea del Castagno.
There are also busts of Giotto and Brunelleschi, besides that of Dante holding the Divine Comedy in his hand. An ideal path, dedicated to the Virgin Mary, goes from pole to opposite pole through the church: the assumption of Mary in Heaven is both in the mosaic over the main entrance as well as in Donatello's work in the round window of main altar the only one of the eight circular windows around the base of the dome that is visible, as soon as you enter the church.
The Duomo of Florence is the richest church in Italy in terms of stained glass windows: out of a total of 55 windows, there are a good 44 that are magnificently decorated and are among the most important works of their kind in Italy. They were based on designs of the principal artists of the period among them Donatello, Lorenzo Ghiberti, Paolo Uccello and Andrea del Castagno.