…wikipedia.org/…/File:Siege_of_La_Rochelle_1881_H…

This Wikipedia page mentions this sci-fy-looking dike actually existed.

Henri Paul Motte French painter, drawer and engraver 1846 (baptised) - 25 March 1922

Richelieu in the center is represented on a dike. At his side, in retreat, his general staff. This dike, which no longer exists today, was built at the time of the Great Siege in 1628 to prevent aid from the English to the Rochelais. Note the particular costume of Richelieu which combines at the same time the armor and the scarlet cape of a Cardinal.

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First Seawall Second Seawall

Four thousand workmen also built a 1,400 meters (0.9 mi) long seawall to block the seaward access between the city and harbor, stopping all supplies. The initial idea for blocking the channel came from the Italian engineer Pompeo Targone, but his structure was broken by winter weather, before the idea was taken up by the royal architect Clément Métezeau in November 1627. The wall was built on a foundation of sunken hulks filled with rubble.