Stupa is a symbolic representation for the level of awareness of humanity. It is in just the same way as the mountain of awareness presentation. As a member of humanity become more spiritually evolved. He will become less dense with a finner vibration. Accordingly then his level of awareness or consciousness will rise. Lower humanity is at the bottom. Middle section is for average humanity. Top section is for higher man; who eventually become lost to the material world as a fully dissolved being.
As the evolution of spiritual consciousness is resisted by the personality or ego; the net result is that all average humanity who are ruled by their ego’s are entrapped within a prison. Insight meditation or serious meditation is a direct comparison to many of the superficial forms of meditation that are available today.