Making different parts of levels look smooth

New, sorry, but I’m having trouble matching up one part of the level to another. It’s a hidden door that will slide up, and behind it will be a cave to another part of the level. square door, round cave, I cant get them to match up correctly. This may be due to the fact that I built the initial room in unity with building block pieces made in blender. I just cant seem to get dimensions right. Should I design the whole level as one .blend file and just import it that way? or is there some trick to matching up doorways in unity that I don’t know about?

Thanks

It’s really hard to get perfectly accurate vertex alignment in Unity. You can get perfect alignment if you build everything on a grid and use grid snaps, but the easiest is probably to build the cave wall and the secret door into the same blender file.