Just a short walk from Sydney's world-famous opera house is the equally impressive, and much older, Royal Botanic Gardens.
The oldest astronomical center in Australia, the Sydney Observatory has a long and glorious history of scientific endeavors. Now converted to a museum and educational facility, it's officially part of the Powerhouse science museum complex.
Located on the eastern side of Darling Harbor, the Sydney Aquarium displays more than 650 species in a unique setting. Even discounting the extraordinary views outside, the more than 6,000 individuals aquatic creatures are housed in unusual style.