It is triangular with a slight natural slope, and is connected to the nearby Piazza del Duomo by an open passage.
The family palace divided the square into two alongside the short axis, thus making this relatively small area a concentrate of medieval architecture.
Originally the area was divided in two squares by the palace and tall tower of the Ridolfi family, the Piazza dell’ Olmo in the inferior and western part and the Piazza delle Taverne in the eastern side and with the cisterna in the middle.
In 1646 the tall Ridolfi tower suddenly collapsed, destroying the palace, so the two squares were merged into one: the Piazza della Cisterna.
The cistern is capped by a travertine octagonal pedestal, which was built in 1346 under the mayor Guccio Malavolti, whose coat of arms with the ladder is carved onto the stones, and is close to the center of the square.