There are no big caves, the maximum grate to build is 255 and there were supposed to be more and the lowest grate is 0, and for example in the 21w07a snapshot there is a -60 grate and in the 21w15a snapshot it is as it used to be.

In minecraft snapshot 21w15a the last square is 0 as in the old ones and in minecraft 1.16.5 version there is a limit to building 255 tiles as it used to be, please fix it because there are no big, very nice and cool caves 😞 this is a very big mistake.