Marco Carelli was a Duomo benefactor and was probably born in Milan between 1320 and 1327. Having renounced his father's inheritance for reasons unknown to us, as a young man he pursued a life in trade, in which he was very skillful. Whether on his own or together with his uncles and cousins, he traded in wool, silk, cotton, leather, wax, sugar powder as well as the products of the lands owned by him, which grew more and more as his activities progressed. In addition to being a merchant, Carelli was also an active financier, and lent money to important families, including the lords of Milan. He married twice: to Giovannina Settala, who died in 1380-81, and to Flora de Liprandis (1386), who survived him, and inherited some properties. He died in 1394. Having had no children, with his will and testament dated July 4th, 1393, and a later addition dated January 26th, 1394, Carelli named as his sole heir the Fabbrica del Duomo, thus becoming, given the size of his estate – at the time valued at over 35,000 ducats, which today would be approximately €30 million - the largest benefactor of all time. He required the Fabbrica to establish a chantry with a daily mass for the repose of his soul to be celebrated at a brand new altar that was to be raised in the Duomo, and a mass to be held on the first day of every month, which was to be officiated by the Metropolitan Chapter. He was first buried in the Church of Santa Maria Annunciata in Camposanto and later transferred to the Duomo, where he still rests. Carelli was dedicated a spire, the oldest, that bears his name. Many documents regarding Carelli are kept in the Fabbrica Archives and mostly concern the forming of his estate and its size, as well as the extremely detailed accounting kept by the Fabbrica after coming into the inheritance.