On the right side of the Duomo's façade one can spot the Astrological Sundial, a solar timepiece sporting the twelve Zodiac symbols arranged on two columns. At its top stands Capricorn, representing the winter solstice, while at the opposite end stands the summer solstice sign of Cancer. A vertical arrow flying from top to bottom extends between the two, while a horizontal line connects the equinoctial signs: Aries (spring equinox) and Libra (autumnal equinox). The structure thus formed is known as a "Zodiac Cross", providing an astrological basis for the conventional birth date of Jesus (December 25, near the hibernal solstice) and a visual reference to the instrument of the Christ's Passion.