Tucked along Darling Harbour, SEA LIFE Sydney Aquarium is a reliable winner with families and anyone dodging a rainy afternoon. You walk through glass tunnels while sharks and rays glide overhead, meet the resident dugongs and get eye to eye with little penguins. It is one of the few places in the city to see platypus up close. Go on a weekday morning to beat the school groups, and use a skip-the-line ticket so you are straight in rather than queueing along the waterfront.