The Bronx Zoo's "World of Birds", a two-story bird house completed in 1972, is a huge, landscaped, indoor free-flight exhibit. The one-way flow pattern in the exhibit moves the visitors through twenty-five birds habitats, ranging from desert to tropical forest. Each setting recreates with impressive fidelity the microculture of the birds that fly merrily about within their diorama world, complete with living plants. Five of the aviaries are completely open: in two of the largest the uncaged public walks through the habitat with birds freely overhead.