The clock takes the form of a sundial and is positioned on the front of the Church of Santa Maria Novella, a Dominican friary, in Florence, Italy. The first Dominican church was begun in the 1220s, but the current façade was constructed under Leone Battista Alberti, the foremost architect of the fifteenth century Renaissance.
The clock, which was commissioned by Cosimo I de Medici, Grand Duke of Tuscany in 1572, consists of a slab of marble, set at right angles to the façade. During the hours before the meridian, the time can be told on the right side, and, post meridian on the left side. Inscribed on the marble are lines and numbers, which allow the shadow of the gnomen to fall in the appropriate place for telling the time in Florence, in Constantinople and also the astrological hours.