evocative room with cross vault supported by granite columns, housing tombs and sarcophagi of Roman, Byzantine and Norman ages. People buried here include archbishops Walter Ophamil, the church's founder, and Giovanni Paternò, patron of Antonello Gagini who sculpted the image on his tomb. The Cathedral Treasury contains goblets, vestments, monstrances, a 14th-century breviary and the famous Crown of Constance of Sicily, a golden tiara found in her tomb in 1491. The cathedral has a meridian, which may be considered as an earlier type of heliometer (solar "observatory"), one of a number constructed in Italian churches, mainly in the 17th and 18th centuries. This one was built in 1801 by the famous astronomer Giuseppe Piazzi, the director of the Observatory of Palermo who discovered the first minor planet or asteroid, Ceres. The device itself is quite simple: a tiny hole in one of the minor domes acts as pinhole camera, projecting an image of the sun onto the floor ). There is a bronze line, la meridiana on the floor, running precisely N/S. At solar noon (circa 12:00 in winter, 13:00 in summer), the sun image passes through this line. At different times of the year the passage occurs at different point of the line. The ends of the line mark the positions at the summer and winter solstices; signs of the zodiac show various dates throughout the year. The purpose of the instrument was to standardise the measurement of time and the calendar. The convention in Sicily had been that the (24-hour) day was measured from the moment of sun-rise, which of course meant that no two locations had the same time and, more importantly, did not have the same time as in St. Peter's Basilica in Rome. It was also important to know when the Vernal equinox occurred, to provide the correct date for Easter. On the belltowers there were six medieval bells. The instrument could be used for research on the apparent movements of the Sun, including its relative distance from the Earth, measured through the size of the floor projected solar disk, and even to compare the results with Ptolemaic and Copernician predictions. 18th and 19th century renovations The church is composed of different styles, as in the following centuries it underwent various changes. The last was at the end of the 18th century, when it radically remade the interior designed by Ferdinando Fuga. In 1767, the