The Tour du Guet ( Watch Tower ) , situated in Calais Nord on the Places d'Armes , is one of the few surviving pre-war buildings . Dating from 1229 , when Philip I , Count of Boulogne , built the fortifications of Calais , it is one of the oldest monuments of Calais , although the oldest remaining traces date to 1302 . It has a height of 35 – 39 metres ( sources differ ) . An earthquake in 1580 split the tower in two , and at one time it threatened to collapse completely . The tower was repaired in 1606 , and then had the purpose of serving as a hall to accommodate the merchants of Calais . It was damaged in 1658 when a young stable boy set fire to it , while it was temporarily being used as royal stables during a visit of King Louis XIV . It was not repaired for some 30 years . In 1770 , a bell identical to the original bell of 1348 was cast . Due to its height , from the late 17th century it became an important watchout post for the city for centuries until 1905 ; the last keeper of the tower was forced to leave in 1926 . Abraham Chappe , ( a brother of Ignace Chappe ) installed a telegraph office in the tower in 1816 and operated for 32 years . It was this office which announced the death of Napoleon I to the French public in 1821 . It also had the dual function as lighthouse with a rotating beacon fuelled by oil from 1818 . The lantern was finally replaced by a new lighthouse on 15 October 1848 . During the First World War , it served as a military observation post and narrowly missed destruction during World War II . This tower has been classified as a historic monument since 6 November 1931
earthquake in 1580
1580 Dover Straits earthquake
Calais