Viewing Ring in Sydney

Set more than 20 m above a lake in an abandoned quarry and with a diameter of roughly 180 m, this circular steel structure serves as a platform for observing the threatened golden tree frog, which has made its home in this biotope. Laid out along the ring are telescopes and an exhibition on the history of the quarry and the evolution of the amphibians who live there. The information is printed on the glazing of the outer wall, which consists of transparent glass panels and perforated aluminium sheeting. The slender steel structure com-prises 26 cruciform supporting elements tied together at the top and the points of intersection and braced by steel cables. Access is via two bridges from the edge of the quarry.