Construction of Notre-Dame started in 1163 and was essentially completed 1240's with some more stuff from 1250-1345. (That's about how it seems that some minor public works projects take to complete these days). I read that new bells designed to replicate the original bells' sound have been installed this year; the largest one which remains from the past is called Emmanuel and weighs 13,271 kg. It tolled in 1944 when French and Allied troops started the retaking of Paris.
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