I remember seeing these on The New Inventors last year.
You're right Corn, they are a little pricey, but may offset the cost of something else like fencing, maybe even a pump system...I could see they'd have there uses in urban design, but you'd have to weigh up their competitiveness with the numerous slimline tanks on the market these days which are a bit less costly.
Cheers for the link.
The real path to natural farming requires that a person know what unaltered nature is, so that he or she can instinctively understand what needs to be done—and what must not be done—to work in harmony with its processes. - Masanobu Fukuoka