The French government is moving its ministry of defence, pulling a whole gaggle of institutions together into a “French Pentagon” to be built on an old Navy site in the suburbs of Paris. Obviously there are the usual complaints, but this is interesting. Jean-Dominique Merchet’s Sécret Défense reports that they are going to knock down a giant circular water tank with a huge rotating arm. Eh?

Well, the site was the R&D centre for French naval shipbuilding, and the installation was used to test the hull design of new ships. A scale model (“scale model” here means something that weighs about as much as an articulated truck) would be built and spun through the water at high speed on the end of the arm, driven by huge electric motors, so the engineers could observe the turbulence it created in the water. The thing is 60 metres in radius, 5.5 metres deep, and the arm moves at 17 degrees a second

These days, we can solve fluid dynamics problems with a Really Big Computer instead, so the thing is losing some of its relevance. But it seems a shame to flatten it and build offices; someone really ought to get some photos taken before the bulldozers move in. A few are here and they are suitably science-fictional.