Then, Brother Gerbert, who later became Pope Sylvester II, invented a simple mechanism in 966 that rang bells at regular intervals throughout the day to call his brethren to prayer. It was the beginning of mechanical clocks as we know them today.
Soon, cathedral towers were providing the rest of the faithful with their first glimpse of a right proper (although not always accurate) mechanical clock.
The earliest of these is credited to Jacopo de Dondi, who designed an astronomical clock for the cathedral tower in Padua in 1344. Curiously, almost every zodiac sign surrounds the clock face except for the balanced scales of Libra. (As the story goes, it was deliberately left out of the lineup by guild workers who felt they weren't treated fairly in salary negotiations.)
Strasbourg Cathedral's mechancial clock appeared in 1354, and was followed by the third, and most elaborate mechanical clock, built in Prague's Town Hall in 1410.
This being the Middle Ages, the Prague clock depicted earth at the center of the universe - with the sun, moon, and stars revolving around it. Blue and red halves separated day and night. With embellishments added over the centuries, today the clock remains a veritable funhouse of timekeeping.