Concrete "trees," steel and wood "canopies," and naval-strength rope "vines" are just some of the ruggedly playful features the architecture firm Iredale Pedersen Hook placed in the Perth Zoo's orangutan habitat. The steel and wood shelters, which sit atop nearly 40-foot-tall concrete poles, were specifically designed to accommodate the tree-dwelling primates' sleeping nests. The exhibit is also eco-friendly: much of it is made of recycled materials, including ropes from decommissioned naval vessels and concrete poles from power companies. However, we're glad the architects didn't take the job too seriously. In what they call a "[behavioral] enrichment activity," the orangutans can spray each other with water cannons mounted on the nesting platforms.