The Basilica di Santa Maria del Fiore (in English, the Basilica of St. Mary of the Flower) is the mother church of the Archdiocese of Florence, in Italy. Constructed in the 14th century, it replaced a fifth-century church on the same spot which was crumbling with age.
The Basilica, with its tall Baptistery of St. John adjacent to the main church, is one of the world’s largest houses of worship. Particularly noteworthy is its Duomo (Dome), which was for centuries the largest dome in the world, and which remains the largest brick dome ever constructed.
How did workmen in the Middle Ages, without modern construction equipment, accomplish such a project?
Politics prevented the use of buttresses, such as were used in nations to the north, because the Italian government eschewed the construction in northern regions and regarded that style of architecture as inferior. The building of such a masonry dome had never been attempted.
What could they do?
This brief video explains better than anything I’ve read how Brunelleschi and other Italian architects met the challenge.