To add to the previous explanations - here's an animation how a 13-meter tall bridge in Prague was built in roughly 60 years (Charle's Bridge). It's an official reconstruction of the local historic society how it was built. Should answer some questions. IIRC it started 1348 and was opened 1407. (not sure about it and too lazy to check it)

https://www.youtube.com/watch?v=nJgD6gyi0Wk

Edit> 1357 - 1402, meeting was less important so I actually checked it :D