7 August 1420 – Construction of the Dome of Santa Maria del Fiore begins in Florence.

The “Cattedrale di Santa Maria del Fiore” (Cathedral of Saint Mary of the Flower) is the main church of Florence, Italy. “Il Duomo di Firenze”, as it is ordinarily called, was begun in 1296 and completed in 1436 with the dome engineered by Filippo Brunelleschi

The cathedral complex, located in Piazza del Duomo, includes the Baptistery and Giotto’s Campanile, three buildings that are part of the UNESCO World Heritage Site covering the historic centre of Florence .
The basilica is one of Italy’s largest churches, and until development of new structural materials in the modern era, the dome was the largest in the world (it remains the largest brick dome ever constructed)

Filippo Brunelleschi, supported by Cosimo de Medici won the architectural design competition for erecting the dome. Until that date the roof of the cathedral showed an enormous hole because no one seemed to have a feasible idea of how to build a dome of that size – which prevented the traditional methods of construction – atop the existing walls, avoiding the flying buttresses and pointed arches of the traditional Gothic style.
The construction of the Dome began on 7 August 142.
It was one of the most impressive projects of the Renaissance: the first ‘octagonal’ dome in history to be built without a temporary wooden supporting frame. The whole structure of the dome – a double shell supported by robust pillars – was designed to be light and slim in both form and substance.