text: zytglogge the zytglogge ( bernese german : / ˈt ͡ / ) tower is a landmark medieval tower in bern , switzerland . built in the early 13th century , it has served the city as guard tower , prison , clock tower , centre of urban life and civic memorial . despite the many redecorations and renovations it has undergone in its 800 years of existence , the zytglogge is one of bern 's most recognisable symbols and , with its 15th - century astronomical clock , a major tourist attraction . it is a heritage site of national significance , and part of the old city of bern , a unesco world cultural heritage site . history when it was built around 1218 – 20 , the zytglogge served as the gate tower of bern 's western fortifications . these were erected after the city 's first westward expansion following its de facto independence from the empire . at that time , the zytglogge was a squat building of only 16 metres ( 52 ft ) in height . when the rapid growth of the city and the further expansion of the fortifications ( up to the ) relegated the tower to second - line status at around 1270 – 75 , it was heightened by 7 metres ( 23 ft ) to overlook the surrounding houses . only after the city 's western defences were extended again in 1344 – 46 up to the now - destroyed , the zytglogge was converted to a women 's prison , notably housing – " priests ' whores " , women convicted of sexual relations with clerics . at this time , the zytglogge also received its first slanted roof . in the great fire of 1405 , the tower burnt out completely . it suffered severe structural damage that required thorough repairs , which were not complete until after the last restoration in 1983 . the prison cells were abandoned and a clock was first installed above the gate in the early 15th century , probably including a simple astronomical clock and musical mechanism . this clock , together with the great bell cast in 1405 , gave the zytglogge its name , which in bernese german means " time bell " . in the late 15th century , the zytglogge and the other bernese gate towers were extended and decorated after the burgundian romantic fashion . the zytglogge received a new lantern ( including the metal visible today ) , four decorative corner towerlets , heraldic decorations and probably its stair tower . the astronomical clock was extended to its current state . in 1527 – 30 , the clockwork was completely rebuilt by kaspar brunner , and the gateway was to provide a secure foundation for the heavy machinery . the zytglogge 's exterior was repainted by gotthard and kaspar in 1607 – 10 , who introduced the large clock faces that now dominate the east and west façades of the tower . the corner towerlets were removed again some time before 1603 . in 1770 – 71 , the zytglogge was renovated by niklaus and ludwig emanuel zehnder , who refurbished the structure in order to suit the tastes of the late baroque , giving the tower its contemporary outline . both façades were again repainted in the rococo style by rudolf von steiger in 1890 . the idealising historicism of the design came to be disliked in the 20th century , and a 1929 competition produced the façade designs visible today : on the west façade , victor 's fresco " beginning of time " and on the east façade , a reconstruction of the 1770 design by kurt . in 1981 – 83 , the zytglogge was thoroughly renovated again and generally restored to its 1770 appearance . in the advent season and from easter until the end of october , it is illuminated after dusk . name the bernese german zytglogge translates to in standard german and to time bell in english ; ' ' means ' bell ' in german , as in the related term ' glockenspiel ' . a " time bell " was one of the earliest public timekeeping devices , consisting of a clockwork connected to a hammer that rang a small bell at the full hour . such a device was installed in the in bern – the tower of the church which the münster later replaced – in 1383 at the latest ; it alerted the bell - ringer to ring the tower bells . the name of zytglogge was first recorded in 1413 . previously , the tower was referred to as the ( " cage " , i.e. , prison ) and after its post - 1405 reconstruction , the ( " new tower " ) . exterior external structure the zytglogge has an overall height of 54 . 5 metres ( 179 ft ) , and a height of 24 metres ( 79 ft ) up to the roof - edge . its rectangular floor plan measures 11 . 2 by 10 . 75 metres ( 36 . 7 by 35 . 3 ft ) . the wall strengths vary widely , ranging from 260 centimetres ( 100 in ) in the west , where the tower formed part of the city walls , to 65 centimetres ( 26 in ) in the east . the outward appearance of the zytglogge is determined by the 1770 renovation . only the late gothic cornice below the roof and the stair tower are visible artifacts of the tower 's earlier history . the main body of the tower is divided into the two - storey plinth , whose exterior is made of alpine limestone , and the three - storey tower shaft sheathed in sandstone . the shaft 's seemingly massive corner blocks are decorative fixtures held in place by visible iron hooks . below the roof , the cornice spans around the still - visible bases of the former corner towerlets . the two - story attic is covered by the sweeping , red - tiled , late gothic spire , in which two spire lights are set to the west and east . they are crowned by ornamental urns with pinecone knobs reconstructed in 1983 from 18th - century drawings . from atop the spire , the wooden pinnacle , copper - sheathed since 1930 , rises an additional 15 metres ( 49 ft ) into the skies , crowned with a gilded knob and a weather vane displaying a cut - out coat of arms of bern . bells and bell - striker the tower 's two namesake bronze bells hang in the cupola at its very top . the great hour bell , cast by johann reber , has remained unchanged since the tower 's reconstruction in 1405 . it has a diameter of 127 centimetres ( 50 in ) , a weight of 1 , 400 kilograms ( 3 , 100 lb ) and rings with a nominal tone of e ' . the inscription on the bell reads , in latin : in the october month of the year 1405 i was cast by master john called reber of aarau . i am vessel and wax , and to all i tell the hours of the day . when the great bell rings out every full hour , struck by a large clockwork - operated hammer , passers - by see a gilded figure in full harness moving its arm to strike it . the larger - than - life figure of bearded chronos , the greek personification of time , is traditionally nicknamed hans von by the bernese . the wooden bell - striker , which has been replaced several times , has been a fixture of the zytglogge since the renewal of the astronomical clock in 1530 , whose clockwork also controls the figure 's motions . the original wooden chronos might have been created by master craftsman albrecht von nürnberg , while the current and most recent hans is a 1930 reconstruction of a baroque original . the bell - striker has been gilded , just like the bells , since 1770 . below the hour bell hangs the smaller quarter - hour bell , also rung by a clockwork hammer . it was cast in 1887 to replace the cracked 1486 original . clock faces and façade decorations both principal façades , east and west , are dominated by massive . the zytglogge 's first clockface was likely located on the plinth , but was moved up to the center of the shaft during the tower 's 15th - century reconfiguration . the eastern clock face features an outer ring of large golden roman numerals , on which the larger hand indicates the hour , and an inner ring on which the smaller hand indicates the minutes . the golden sun on the hour hand is pivot - mounted so that it always faces up . below the clock face one sees an idealised profile of city founder duke berchtold v of zähringen . while the exact decoration of the clockface has varied from renovation to renovation , the current ( post - 1983 ) layout is generally that of 1770 . the western clock face has similar hands , but is an integral part of victor 's 1929 fresco " beginning of time " . the painting depicts chronos swooping down with cape fluttering , and , below the clockface , adam and eve 's eviction from paradise by an angel . astronomical clock the dial of the zytglogge 's astronomical clock is built in the form of an astrolabe . it is backed by a projected planisphere divided into three zones : the black night sky , the deep blue zone of dawn and the light blue day sky . the skies are crisscrossed with the golden lines of the horizon , dawn , the tropics and the temporal hours , which divide the time of daylight into twelve hours whose length varies with the time of year . around the planisphere moves the rete , a web - like metal cutout representing the zodiac , which also features a julian calendar dial . above the rete , a display indicates the day of the week . because leap days are not supported by the clockwork , the calendar hand has to be reset manually each leap year on 29 february . a moon dial circles the inner ring of the zodiac , displaying the moon phase . the principal hand of the clock indicates the time of day on the outer ring of 24 golden roman numerals , which run twice from i to xii . it features two suns , the smaller one indicating the date on the rete 's calendar dial . the larger one circles the zodiac at one revolution per year and also rotates across the planisphere once per day . its crossing of the horizon and dawn lines twice per day allows the timing of sunrise , dawn , dusk and sunset . the painted frieze above the astronomical clock shows five deities from classical antiquity , each representing both a day of the week and a planet in their order according to ptolemaic cosmology . from left to right , they are : saturn with sickle and club for saturday , jupiter with thunderbolts for thursday , mars with sword and shield for tuesday , venus with cupid for friday and mercury with staff and bag for wednesday . the painting of the entire clock area was refurbished in 1983 . only the matte areas on the clock face are from the earlier coat of paint . movement the clock dial has been dated to either the building phases of 1405 or 1467 - 83 , or to the installation of the brunner clockwork in 1527 - 30 . notes that the planisphere uses a southern projection , as was characteristic for 15th - century astronomical clocks ; all later such clocks use a northern projection . this would seem to confirm the dating of the clock to the 1405 or 1467 / 83 renovations . a clock is documented in this tower since 1405 , when a new bell was installed . the city accounts of 1438 mention the repair of the clockworks . the first mention of a dial is in 1443 , and the first known image of the , much smaller first dial ( in the diary a cobbler journeyman from ulm ) is dated 1534 . the ( ) is also documented in the same 1534 source . in the first two decades of the sixteenth century many craftsman unsuccessfully tried to improve the clockworks . the current movement was made in 1530 by clockmaker kasper bruner and is dated and signed by a forged nameplate . no other clockworks by this master are known . the core of the movement was forged in - situ , in the very room it is still located , and the fire pit of the forge remains in the room . one of the more unusual features of the movement is that each individual tooth of the major gears is removable ( as it wears ) . originally the movement had a verge escapement with a foliot , as it was built 127 years before the pendulum clock was invented . the zytglogge movement was converted to a much more accurate pendulum mechanism by the french clockmaker pierre between 1686 and 1688 . the current pendulum bob , a " recycled " iron cannonball , possibly dates from that time . the pendulum suspension is made from leather rather than using a metal spring . the weight - driven movement is wound daily by hand . that task , a role known as the " " , has been held for over 25 years by the same individual . interior the zytglogge 's internal layout has changed over time to reflect the tower 's change of purpose from guard tower to city prison to clock tower . the thirteenth - century guard tower was not much more than a hollow shell of walls that was open towards the city in the east . only in the fourteenth century was a layer of four storeys inserted . the rooms above the clockwork mechanism were used by the city administration for various purposes up until the late 20th century , including as archives , storerooms , as a firehose magazine and even as an air raid shelter . the interior was frequently remodelled in a careless , even fashion ; for instance , all but three of the original wooden beams supporting the intermediate floors were destroyed . since 1979 , the tower 's interior is empty again . it is only accessed for maintenance and in the course of regular guided tours .