Gravitational singularity
An example would be that if a person were to stand on a collapsing star right before the singularity forms, and they sent a signal every second to a nearby observer, time and space would slow down as the singularity is being formed. The observer would hear the signal slowing down. Let's say the singularity forms at 12:00 exactly. The observer would receive all the signals, one after another, with each new signal slowing down at a very small rate until the 12:00 signal. When the 12:00 signal was sent, time and space would be infinite -- in other words, it would take forever to get the signal.