The Penrose diagrams have been used rather successfully in describing flat spacetime, especially in the simplified case of one space dimension. They have also been used to depict the influence of a black hole on these diagrams. I am proposing a revision to this depiction with the below diagram which demonstrates more clearly the impact of a black hole on spacetime when gravity takes over and essentially collapses spacetime into a singularity.
In the past when using Penrose diagrams, the addition of the black hole quadrant was placed on the same one dimensional plane, in the below diagram it is depicted as an extension (dotted lines) downwards coming to a point below the center point on the original diagram. This extension downward demonstrates the intense gravity exerted by a black hole that brings spacetime to a stationary state. In other words, time does not exist because space is not in motion but rather is stationary (see November 2022 posts in this blog which delineate this concept (4 states of space) in greater detail and see the abstract below).
I apologize in advance for the crudeness of the drawing but I think it captures the revision I am suggesting. I will leave it to graphical artists to add the artistic details.
Here is an abstract of taking the above proposal and applying it to an expansion of the four states of space proposal: