Textured ceilings probably help hide things, but why the lines?
People being confidently wrong in the comments again. It’s the seam between two pre-cast hollow-core slabs. This is how every single apartment building is built at where I live.
My garage was constructed with those at my old house. Allows you to have usable space under the garage. But it leaks when they install incorrectly – no membrane was installed on the top side and they put the lumber walls on the same cement block as the spancrete. They are supposed to build up a half course of cement block so that the base of the lumber walls sits higher than the garage floor.
People being confidently wrong in the comments again
Lol! Every thread. Can’t say I haven’t been that person, too. 😅