This was the home of Francesco di Marco Datini (1330-1410), a textile magnate and secular patron saint of capitalism whose life was drawn so vividly by Italian-American author Iris Origo that he's become known by the title of her book, The Merchant of Prato. Datini invented the promissory note, and he kept scrupulous records of all his business activities -- the basis for Origo's book -- and inscribed each one of his ledgers with an accountant's battle cry: "For God and Profit."
One of the few places he allowed himself to spend money was on the decoration of his home, hiring Niccolò Gerini and Arrigo di Niccolò di Prato for the job. The outside frescoes have faded to reveal fascinating sinopie (preparatory sketches) underneath -- though what you see on the façade is a copy (originals are in the archive). However, many paintings on the interior walls remain. The ticket room retains bucolic scenes bubbling with plant and animal life, and a side room contains a portrait of Datini. Next to the door, as in many medieval houses, is a giant St. Christopher, which Datini glanced at daily to protect against sudden death while he was out conducting business.