One of my favorite "WTF" engineering moments is the Atlantropa Project, a proposed draining of the Mediterranean Sea. A series of dams at Gibraltar and the Dardanelles (and other places) would cut the flow of water into the Mediterranean, and evaporation would do the rest draining the seabed. It was initially proposed in the 1920s and was discussed into the 1950s before it was abandoned.
The goal was to provide lebensraum for European populations without all of that killing of the ubermensch nastiness that we saw in der tausandjarische Reich. New land would have been settled and planted, and roads and railroads would connect the new areas with Europe and Africa. A new era of pan-European pacifism would bind a continent shattered by the War To End All Wars.
The likelihood of the Sahara desert colonizing the new land seems not to have been considered, not the chance of loss of rainfall in the lands bordering the receding sea. It is a breathlessly reckless example of engineering hubris, best captured in this classic XKCD cartoon:
Simpler times. Today there is a global project to "save the planet" from the horrors of carbon dioxide. Much more sophisticated than Herr Sörgel and company. So much more. And so much less naive on the healing power of pacifism and Big pan-Governmental projects. I mean, we can see his hubris, can't we?