Answer:
The afterlife
Step-by-step explanation:
Hamlet is thinking of killing himself that will take his life. However, his teaching thwarts him of what will happen afterlife, which is a place that people travel and never get back. In this scenario, he was referring to a state of death.
However, he has hesitation from his little knowledge about death since nobody had explored the idea has ever returned. Therefore this is a famous metaphor that had been in existence since exploration. Thus his plight will not be solved by traveling to the undiscovered land.