Beauty is in the eye of the beholder, right?
Sydney is a large metropolis but does have some world wide attractions.
Sydney opera house has tours.
You can take a ferry across the bay to the Taronga zoo to see all the different species native to Australia along with the regular zoo stuff.
There's the Skyfeast rotating restaurant in Sydney Tower.
https://skyfeastsydneytower.com.au/
Of course a bunch of beaches. Be prepared for heat as it will be summer at new years.
If planning on multiple stops:
Port Douglas (N of Cairns) has nice beaches and access to the Great Barrier Reef.
Brisbane is on the "Gold Coast" and is more tropical like Florida or Hawaii.
Canberra, capital of Australia, is really unique as the city center was completely designed before constructed.
If you want to see New Zealand watch the Lord of the Rings.