Cairns

Cairns needs 3 days, almost entirely organized around boat trips to the Great Barrier Reef. June-October is the dry season, with better underwater visibility and less tropical humidity. It's expensive by Australian standards given its role as the tourist gateway to the reef. It's the main base for accessing the Great Barrier Reef, the world's largest coral reef system and one of the most biodiverse marine ecosystems on the planet, visible even from space.