week on "global ideas," we head to south africa, where ade are key to water supply too highly to bethe economy. every day, thousands of refrigerated lorries carrying perishable goods hit the roads. most of them use environmentally-toxic cooling agents, and they're also often poorly insulated. by substituting natural coolants and using improved technologies, refrigerated transport is set to become a whole lot greener. you'll find all that and more on next week's edition. that's all for today, but we love hearing from you. drop us a line to global3000@dw.com or visit us on facebook -- dw global society. bye for now. [captioning performed by the national captioning institute, which is responsible for its caption content and accuracy. visit ncicap.org] nsteves: we're in rothenburg,, germany's ultimate walled city. in the middle ages, when frankfurt and munich were just wide spots on the road, rothenburg was one of germany's largest cities, with a whopping population of 6,000. today, even with its crowds and overpriced souvenirs, i love this place. during rothenburg's heyday -- that was about 1200