Short answers, pulled from the story.
Evidence points to a major project beginning in the early 1070s, likely under the supervision of Bishop Ranieri who took office in 1072 or 1073. Construction continued well into the 12th century even if the building was in use by the late 1080s.
A hypothesis published in 2024 suggests powerful rulers Beatrice of Lorraine and her daughter Matilda of Tuscany sponsored the work alongside Pope Gregory VII. Florence at the time was too small to afford such an ambitious project alone.
The shape holds deep theological significance beyond mere aesthetics as theologians call the eighth day eternal life beyond measurable time. This concept aligns with early Christian examples like the fourth-century Battistero Paleocristiano beneath Milan Cathedral and the fifth-century Lateran Baptistery.
Work lasted from 1429 until 1447 and cost almost as much as Florence's purchase of Sansepolcro. Ghiberti's salary equaled that of a Medici bank manager during this period.
Giovanni Villani records that the lantern atop the dome was completed in 1150, marking the first known example of this element in architectural history. The south portal reliefs by Andrea Pisano took six years to complete, with the year 1330 appearing above the doors.