One of the largest such projects was the Zuiderzee works, which closed a large inlet of the North Sea. Then (according to the table in the Wikipedia page), 1650 km^2 land was claimed from the sea (the land was large enough to add a new province to The Netherlands in 1986).
Even though (AFAIK) the timeline was not exactly laid out, it was clear from the outset that this project would take many decades.
The scale of the Zuiderzee works is really insane. Even building of the dyke that encloses the inlet was projected to cost a year of the national budget.
Even though (AFAIK) the timeline was not exactly laid out, it was clear from the outset that this project would take many decades.
The scale of the Zuiderzee works is really insane. Even building of the dyke that encloses the inlet was projected to cost a year of the national budget.
https://en.wikipedia.org/wiki/Zuiderzee_Works