Who: Innovator in Residence, Zoz Brooks
What: Zen Garden
Where: Cambridge, MA
How: Fill the outer ring with sand, and the inner one with water. The gas filters up through the sand and bubbles up through the water, once it gets into the air it can ignite. It combines the four alchemical elements: earth (sand), air, water and fire.

People were then given rakes to interact with it. The flame patterns collect in the troughs of the raked sand, so they could draw designs or patterns or whatever the wished, and see them illuminated in flames. It ran for about 12 hours!

Zoz started off with 6 tanks of propane (standard BBQ size) and  he probably used about 4 of them during about 11-12 hours of running it, the tanks started to freeze up from continuous use, so he had to swap them in and out (and dunk them in a trash can full of water) so only 2 were completely emptied.

Caution: Do not try this at home! Professionals only.