The following is an excerpt from “The Benefits and Practices related to Statues and Stupas” by Lama Zopa Rinpoche
The conclusion for Buddhists and non-Buddhists alike is that the stupa is a way to purify defilements. A holy stupa is a way to benefit sentient beings without words. It will liberate beings from samsara in silence. To have such a holy object existing in a country makes it very rich and very lucky. Many people will come to visit for pleasure as tourists, but it will at the same time make their life meaningful. The most important point is that holy objects help beings to purify their mind and to collect extensive merit so that it is possible for them to easily have realizations of the path. That is the main function of these holy objects – to help us sentient beings have quick realizations of the path to enlightenment by the power of the holy object.
Those who build and work to actualize those holy objects will bring these beings to enlightenment. So anyone who sees it, touches it, remembers it, even dreams of it will have the seed planted for their own enlightenment. As well, prostrating and so on to the stupa helps bring them to enlightenment. By have the Secret Relic mantra within the stupa, any animals, ants, butterflies, etc. that go around the stupa even just once are purified of their negative karma to be born in the hot hells.
Even if we all die, as long as the holy objects that we have created last, our work, our effort [to create holy objects], is still benefitting sentient beings continuously. For all the many hundreds and thousands of years that the stupa will last, every day it will liberate sentient beings in silence…without words…without our talking Dharma to them. You see, just by seeing the stupa, the minds of of sentient beings who come here get purified. So many negative karmas get purified. Even the insects who are killed by machines during the construction – even they will not be reborn in the lower realms. Even those that die during the building process will receive a good rebirth. It is mentioned by a great Indian teacher in a text calledMatasara, or something like that, that even if you make food for the people building the temple, your negative karma will be purified.