History of the Duomo Milan in a Nutshell
In 1385, with the aim to replace the existing cathedral on site, a new one was commissioned by Giangaleazzo Visconti. The work had begun in 1386, but soon in 1402 it had all stopped due to a shortage of funds and lack of ideation.
In 1805, Napoleon Bonaparte helped in financing the construction and much more of the cathedral was built including the pinnacles, spires, flying buttresses, and the roof. The flying buttresses are pillars that form an arch with the walls they support often topped with vertical ornamentation.
New stained-glass windows were made between 1829 and 1858 to replace the existing ones. In 1943, the city was bombed, which ended up impacting the church and it had to be repaired. The construction of the church was not completed until 1965 when the construction was finally done and the cathedral was open to the public.