From his election in 1572 to his death in 1585, Pope Gregory XIII spent a great deal of money on the building and restoration of Rome's streets, churches and public monuments. One major monument, the three-story apartment rising from the Vatican Palace called the Tower of the Winds, was built to celebrate the most famous achievement of Gregory's papacy, the calendar reform. Its innovations in architecture and decoration and its wider religious and political purpose are the subject of this book.