Good find by flb, Noisette, kite_surfer, carmedic, BridgePlayer and redunzl.

ANSWER: >> National Botanic Garden, near Llanarthney in the Towy Valley, Carmanthenshire, Wales, UK. The largest single-span greenhouse in the world, the Glasshouse contains more than a thousand plant species � many endangered � and conserves specimens from warm climates around the globe. The laminated glass roof's torodial form measures 99 m x 55 m and swells from the ground like a grassy hillock, echoing the undulations of the surrounding landscape. (reported by Laminated Glass News, www.dupont.com) <<