SYDNEY TOP 5

1. Sydney Harbor
This should be the first stop on any Sydney itinerary. A visit to the harbor will take in several of Sydney's preeminent sights including the Sydney Opera House and Sydney Harbor Bridge. Take a Sunset Dinner tour on the harbour to appreciate the city from the water.

2. The Sydney Opera House
Explore this iconic building from every possible angle! Take a guided tour for a greater insight into the day-to-day workings of the Opera House and then take in a performance (it's not all Opera you know!).

3. Sydney Harbor Bridge
This magnificent bridge presided over Sydney Harbor way before the Opera House was even a glint in architect J?rn Utzon's eye. You can explore the bridge on foot, climb inside the pylon or take a guided walk over the top (if you dare!).

4. The Royal Botanic Gardens & the Domain
This green oasis enjoys one of Sydney's most spectacular outlooks over the city and Sydney Harbor. Established in 1816, the gardens are home to an outstanding collection of plants from Australia and overseas. The Domain surrounds the Royal Botanic Garden and is a popular walking and picnic spot.

5. The Rocks
The Rocks is a shopping and dining area directly west of Sydney harbor that has a fascinating and unique history. It marks the place where Australia's European settlement began and has many historic buildings and sites that offer glimpses into Australia's colonial past

Taronga Zoo is also worth a look. You can get there on a ferry ride across the harbour (well worth it!). There are plenty of great views of Sydney from the zoo and of course lots of aussie animals.

Don't forget to visit Sydney Tower Eye which is just very amazing because you can see the whole city from it, and you can skywalk on the top of that tower with a very affordable price.
Be sure to spend a full day in the Blue Mountains where you can experience a very good adventure, and visiting Sydney Aquarium is must if you're visiting that city for the first time.

Take the ferry to Manly. The beach isn't all that spectacular, but I rented a bike and rode all over North Head. Lots of cool look out points, and beautiful cliffs.

Might I suggest some alternativesos?

Go Scuba Diving in the Sydney blue

Have a hot Christmas beach party instead of the white christmas card image you are used to. Get oiled up and get tanned

Ride in a helicopter PLUS dive out into the sky. I've never done this but I know lots of people who have (usually travellers) and apparently it is epic and unbeatable

Or the chillax version: Hot air ballooning

Whale watching? They are pretty rare, it would be terribly exciting to see them way out there being happier than free willy

Or if you in Oz really soon, an event rather a location.. hit up Australia Day!