Regenstein African Journey, a renovation of the zoo's former Large Mammal House, opened in 2003, turning the zoo's largest building from concrete showcases for a few large mammals into a series of naturalistic settings that tell the story of the wildlife of the African continent, welcoming the return of the zoo's African elephants and giraffes as well as new additions such as the aardvark, ostrich, and African wild dog. Two years later, the zoo renovated its Great Ape House, opening the Regenstein Center for African Apes, which focused on the zoo's troops of common chimpanzees and western lowland gorillas, putting a special emphasis on researching the behaviors of both species and creating new, naturalistic habitats.