 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 <unk> ) relegated the tower to second @-@ line status at around 1270 – 75 , it was heightened by 7 metres ( 23 ft ) to overlook the surrounding houses . 
