One of the small, but significant things I noticed about German apartments was the lipped 'bezel'[1], where the door and the frame fit snugly into each other and there is a rubber/plastic seal between the door and the frame. This is a big deal in an apartment, because it reduces noise, reduces drafts, and eliminates the need to heat more than one room at a time. Also, the door itself seems to be very solid, you'd have to hit it with quite some force to make a dent - none of this cardboard sandwiched between 2 slides of thin MDF nonsense. I'm not from the US, I've just noticed this in Germany coming from another European country with less quality interior finishings.

[1] https://www.reddit.com/r/InteriorDesign/comments/8ths03/germ...