The construction of the Duomo officially started in 1386 and took thousands of workers, a new canal system and over six centuries to complete. The Duomo is the fifth largest Christian church in the world. There are 3,400 statues, 135 gargoyles and 700 figures that decorate Milan Duomo! Above the apse (the arched part above the altar) there is a spot marked with a red lightbulb. This marks the spot where one of the nails of Jesus’ crucifixion was allegedly placed.