Any great Medieval or Renaissance city had to have a cathedral.  A house of worship that gave testimony to not only the piety of the city but its affluence as well.  The Florence Duomo was completed in the early 15th century and took more than 100 years to complete.  The result today is every bit as stunning and awe-inspiring as it must have been then.  It is truly a testament to the wealth, ingenuity and beauty of the Italian Renaissance.