What should I see in Sydney if I only have two days?

Give the first day to the harbour. Start at Circular Quay, walk around the Opera House and Royal Botanic Garden, then cross to The Rocks. If you still have energy, walk the Harbour Bridge pedestrian path for a second perspective; the paid BridgeClimb is a separate choice, not a requirement. Circular Quay and The Rocks give you plenty of places to stop for lunch or dinner without losing time in transit.

On day two, choose one longer outing: take the public ferry to Manly for a beachside meal, or head east for Bondi and a coastal walk. Both are good days, but trying to cover both along with the harbour icons can turn the visit into a timetable. Leave room for the weather and for a neighbourhood you discover along the way.