Although time and its measurement is a fundamental component of human life, a special type of clock which takes matters to the next level is the so-called astronomical clock and whose purpose is not to measure time per se but to convey astronomical information and, in particular, the relative position of the Sun and Moon as well as the zodiacal constellations and, in some cases, the position of the planets all as a function of time.

The oldest such effort to effectively emulate the overhead celestial sphere (ie a mini-planetarium) is the Antikythera Mechanism which was discovered in 1901 totally by accident by sponge divers off the coast of the Greek island of Antikythera. It has been dated to approximately 80 BC and it is believed to be the work of Poseidonius of Rhodes. The Antikythera Mechanism is currently on display at the National Archaeological Museum in Athens, Greece.

Note: With a population of only 55,000 people, Venice is host to approximately 25 to 30 million tourists each year owing to the fact it is generally regarded as one of the most beautiful and romantic cities in the world thanks to stunning architecture, countless water canals and bridges, lively festivals as well as being the birthplace of rennaisance art and music. To this end, Venice is often described as the "City of Canals", the "City of Water", the "City of Masks" and the "City of Bridges" amongst others. Its uniqueness was recognized by UNESCO when the city was incorporated into the catalog of World Heritage Sites in 1987.

The primary square in Venice, Piazza di San Marco (St Mark's Square), is one of the primary attractions in Venice thanks to the Basilica di San Marco, named after the patron saint of the city, and which forms the eastern facade of the square. To the immediate north of the basilica and the square's northeastern quadrant, one will encounter the clock tower ("Torre dell'Orologio") whose construction during 1496-1497 involved the father and son team of Gian Paolo and Gian Carlo Rainieri. Having undergone many restorations during the past 500 years including the latest during 1996-1999, tradition similar to what was practised with other clock towers in Europe saw the presence of a permanent timekeeper (horologist) who lived in the tower (along with his family) so as to service and maintain the clock. This practise would continue for literally 500 years, often involving generations of the same family, and until 1998 when it was finally abandoned.

The design of the clock is very much similar to other clocks of the time with various concentric rings representing the hour of day, the month with the zodiacal constellation the Sun was passing through, phases of the moon etc. More specifically and as can be seen in the photo below, the outer ring is made from marble and has the Roman numerals I through XXIV inscribed and which represent the hour of day starting with "I" between the 3 and 4 o'clock positions of a modern-day clock. The next ring which follows involves the zodiacal constellations with their appropriate symbols in gold colour set against a dark background where a mobile pendant with a golden Sun straddles the outermost two rings indicating the current hour and position of the Sun amongst the zodiacal constellations. A much smaller ring follows for the date of the month with demarcations in five-day segments (ie. "5", "10", "15", "20", "25" and "30"). The innermost disk follows and which contains the Earth at its center due to the prevailing Aristotelian/Ptolemaic geocentric view of the Solar System at the time along with a rotating ring for the Moon undergoing suitable changes in its phase as well as depicting its travels along the zodiac. This ring is set against a blue background reflecting the sky and includes various stars interspersed throughout. The original version of the clock also included the five planets with their own rings so as to be compatible with the Ptolemaic model but were eventually removed with today's version being in its most simplistic form. In fact, it is believed that Galileo was instrumental in having the five planetary rings removed following his invitation to visit Venice and see the newly-built clock.

The clock tower's internals are open to the public and 50-minute guided tours requiring pre-booking are available with groups limited to a maximum of five members due to the tight quarters inside the clock tower.

Note: For a view of the astronomical clock using greater focal length, please click here and here.

Note: For additional results involving astronomical clocks from around the world, please click here.