Once the Sand Mandala is complete, it's ceremoniously swept into a bin and returned to nature. The idea, as I understand it, is to demonstrate how even actions that are impermanent have meaning, symbolic of our transitory lives on this planet. Or, stated another way, "maybe the real Mandala was the friends we made at the sand table."
Then I pointed at a Sand Mandala that was visibly hanging on the wall and asked what's that. They explained that that Mandala was present during a visitation by the Dalai Lama to their temple so they glued the sand in place and hung it up.
I was like, wait, doesn't that invalidate the premise of the Mandala? To which they just kind of shrugged and smirked and said "not really. That one is special, but it too will be destroyed someday."