Engineering feats

I was thinking about these things independently, but it turns out that they have something in common. What we think of as modern engineering feats were often conceived - and sometimes carried out - a century or more ago. Consider the following examples:
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The submarine. Designs for "underwater boats" date back to the 1500s. The 1st serviceable model was built in the 1800s. An illustration of a "rebel infernal machine" (1st image) appeared in Harper's Weekly in 1861. The most famous of these is the Hunley, posthumously named after its inventor, Horace Lawson Hunley (1823-1863). The converted steam boiler sank twice during its trials, taking him with it, but during the American Civil War, Confederates raised it and in 1864 used it to sink Federal steam-powered sloop-of-war the U.S.S. Housatonic in the Charleston, South Carolina, harbor. The Hunley's own fate was unknown until it was rediscovered in the harbor, donated to the State of South Carolina in 1995, and raised in 2000.
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Ship-lengthening. In 2005, the Royal Caribbean cruise ship Enchantment of the Seas underwent an immense transformation in which she was cut in half and a 73' section was added to the middle, which increased the number of cabins by 151 and her length to 990'. The largest cruise ship to be lengthened to date, she was not the first. The stretching of ships became popular in 1871 to accommodate new compound steam engines without losing capacity, and the Allen Line (2nd image) altered many of its ships.
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The Chunnel. The Channel Tunnel linking England and France underwater by high-speed trains opened in 1994, an engineering feat that had broken ground in 1988. But the idea was envisioned as early as 1802, when a French mining engineer proposed to dig a tunnel under the English Channel through which people could be transported by horse-drawn carriage. His plan had a mid-channel island, and an 1856 plan (3rd image) by another Frenchman for a railway tunnel had a mid-channel airshaft.
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To conclude, a bit of trivia about the Chunnel. Did you know that when the French and English tunnel-boring machines met in the middle, some were dismantled, but 3 were driven downward and buried in place?