This site is where you can buy a Klein Bottle, a one-sided three-dimensional container with a volume of zero. (It doesn’t specify if the zero is in liters or gallons, though. A disappointing oversight. I don’t want to end up having to perform metric-to-imperial conversions while calculating how much nothing the thing can’t contain.)
They have to cheat a bit to get the thing into three-dimensional space. The nexus where the handle / neck intersects is displeasing, but it’s a necessary compromise because because most glassblowers refuse to work in four dimensions.
(Yes, I can see this site is ages old, almost prehistoric by internet standards. It’s so old it’s new again. Anyway, I’ve never seen it before.)