Clock
This is the most prominent feature as it suggests that man is trying to control the uncontrollable. By attempting to measure time, Dor is attempting to change the natural cycle of the universe and measure the time that you have as opposed to appreciating it.
Cave
The cave is a strong setting and imagery because it takes us back to the time where time was just starting. The prehistoric era and cavemen times were primitive and time was not something that was measured. By displacing Dor in this time period, he begins to truly appreciate time.
Cryonics
This introduces a new mechanism by which man has tried to control time. The clock building was the first step but now the attempt to control time has taken a further step.This suggests that soon man will take over time.
God
The imagery of god brings back to attention the uncontrollable and immeasureable notion of time. God is a timeless being so his presence denotes the inability of man to ever be able to measure time.