In 1964, I.M. Pei was commissioned by city leaders to create a revitalization plan for downtown Oklahoma City. The area that is now the Myriad Botanical Gardens was originally designed by I.M. Pei to model Tivoli Gardens in Copenhagen. Myriad Gardens feature a 224 foot conservatory (The Crystal Bridge Tropical Conservatory) and built with translucent acrylic panels. It bridges a natural lake and has a 35 foot waterfall, a Rain Forest, a Dry Tropics zone, a Californian Zone, a birdhouse, a reptile house, a fishpond and a sandy beach. A path leads to the top of a mountain, past the source of the waterfall and to a tropical skywalk. The rock formations were made by taking latex molds from real rocks. The internal atmosphere is sometimes hot-dry and sometimes misty-wet. The Crystal Bridge also has a collection of 2000 orchirds, including Dendrobium, Phalaenopsis, Cattleya, Oncidium, Vanda and Paphiopedilum. The outside garden is square in plan but has rolling hills.