How to create a floor system in 2D Top-Down game?

Hello,
I’m developing an Unity 2D game in the style of old Nintendo games. Top-down. One of my favorite games is the escapists, which I was inspired by. In it, you can climb onto the roof to escape.

How to create a floor system in 2D Top-Down game?

I guess the solution to the problem is layers. But since I am a complete novice in Unity, I do not understand how it is possible to display, for example, floor 0 when I am on 3, without colliding with colliders of other floors. As if stepping on a tile, which is a void, you can fall to the 0 floor.

moderator note: add images to illustrate specific issues you want to resolve here


I will be very grateful, I have searched the entire Internet.