not only a giant pool, but it’s in a batcave and it looks like an album cover

I especially liked the part where they designed the sensors inside domes, so they could handle the pressure without any issue. But then when one imploded it caused a cascade failure that destroyed a huge part of the thing. It left the whole thing crippled for years as they struggled on with just a small part of the sensors (which they redistributed and beefed up a bit). Luckily a few years later it got a full upgrade and rebuild, so it was back to 100% again.