Cairns is a city in North Queensland. Apart from being a popular tourist town, it is also dubbed as a the "gateway" other destinations, such as the Great Barrier Reef.
While in Cairns, you can take a walk on the promenade near the lagoon and enjoy the view of the sea.
To visit the world-famous barrier reef, you can take a one-day tour offered by various companies, which takes you to the reef area and you can snorkel, or even scuba dive for a few hours. Underwater disposal cameras are sold but they are usually rather expensive. The view underwater is truly spectacular, with a lot of fish and corals.
Cairns is also the gateway to Kuranda, a small town. To get to Kuranda, you can take the skyrail rainforest cableway, which is a gondola ride consisting of a few stops. It gives you a good view of the canopy of the rainforest.
You can also take the Kuranda Scenic Railway from Cairns Central Station. The train journey takes about one and a half hour. The train would stop briefly for some photo opportunities of the Barron Fall near Kuranda. The Skyrail gondola ride can be combined with the Scenic Rail as a round trip. There is a birdworld in Kuranda, as well as market selling locally produced arts and crafts.
The Cairns Botanical Garden is slightly off Cairns, and quite close to the airport. There, you can find a wide variety of plants. And right next to it is the entrance to the Mt. Whitfield Conservation Park which gives you a good view of the city, as well as the airport. You can see the airplanes landing and taking off.