Answer:
The imagery of “the heart” suggests the relationship between the society which the narrator plans to build on the mountain and the outside world is that:
News of the new society on the mountain will gradually spread to the outside world, and the independent thinkers will come to it.
Explanation:
The above passage is from the last section of "Anthem". In the last lines, the author wants to say that he would build a place which would be away from the present world. His world would be like the heart which will be hidden but would beat and make the world living. Also, he says that this world would be very inclusive for the people who can understand the importance of it.