back on topic, your kitchen floor is curved. Just the curve is ridiculously small (if your kitchen is five meters lengthwise, then a tile at one end is about 1 micrometer below a tile at the other, far, far, far too small to be noticed by eyes or even by precise instruments.
in addition, the houses in romania that were leveled with respect to the house in france would be slightly tilted. Indeed, the neighbor's house would be tilted, although by a mathematically insignificant number of degrees, incidentally also undetectable by a spirit level. People would start to notice roughly one-quarter the way to romania