Outline map of the various hydroelectricity and land reclamation projects combined in Atlantropa.
Sörgel's proposed new locks at the Gibraltar Dam.
The plan was inspired by the then-new understanding of the Messinian salinity crisis, a pan-Mediterranean geological event that took place 5 to 6 million years ago. The contemporary geologists proposed that the large salt deposits surrounding the Mediterranean coast were the result of its partial isolation by a shrinking of the seaways connecting to the Atlantic. Today it is a majority opinion among geoscientists that the Mediterranean underwent a significant drawdown during that period, of at least a few hundred meters.
The Utopian goal was to solve all the major problems of European civilisation by the creation of a new continent, "Atlantropa", consisting of Europe and Africa and to be inhabited by Europeans. Sörgel was convinced that to remain competitive with the Americas and an emerging Oriental "Pan-Asia", Europe must become self-sufficient, and this meant possessing territories in all climate zones. Asia would forever remain a mystery to Europeans, and the British would not be able to maintain their global empire in the long run—hence a common European effort to colonise Africa was necessary. The lowering of the Mediterranean would enable the production of immense amounts of electric power, guaranteeing the growth of industry. Unlike fossil fuels, this power source would not be subject to depletion. Vast tracts of land would be freed for agriculture—including the Sahara desert, which was to be irrigated with the help of three sea-sized man-made lakes throughout Africa. The massive public works, envisioned to go on for more than a century, would relieve unemployment and the acquisition of new land would ease the pressure of overpopulation, which Sörgel thought were the fundamental causes of political unrest in Europe. Sörgel also believed the project's effect on the climate could only be beneficial. Sörgel believed that the climate could be changed for the better as far away as the British isles due to a more effective Gulf Stream creating warmer winters. The Middle East under the control of a consolidated Atlantropa would be an additional energy source and a bulwark against the so called Yellow Peril.
The publicity material produced for Atlantropa by Sörgel and his supporters contain plans, maps, and scale models of several dams and new ports on the Mediterranean, views of the Gibraltar dam crowned by a 400-metre tower designed by Peter Behrens, projections of the growth of agricultural production, sketches for a pan-Atlantropan power grid, and even provision for the protection of Venice as a cultural landmark. Concerns about climate change or earthquakes, when mentioned, were framed as positives rather than negatives. Sörgel's 1938 book Die Drei Grossen A has a quote from Hitler on the flyleaf, demonstrating that the concept was not inconsistent with Nazi ideology.
After the Second World War, interest was piqued again as the Western Allies sought to create closer bonds with Africa and combat communism, but the invention of nuclear power, the cost of rebuilding, and the end of colonialism left Atlantropa technologically unnecessary and politically unfeasible, although the Atlantropa Institute remained in existence until 1960.
Most proposals to dam the Strait of Gibraltar since that time have focused on the hydroelectric potential of such a project, and do not envisage any substantial lowering of the Mediterranean sea level. A new idea involving a tensioned fabric dam stretched between Europe and North Africa in the Gibraltar Strait is envisioned to cope with any future global sea-level rise outside of the Mediterranean Sea Basin.