I think Sydney is boring! Those who don't live in Sydney (especially those from overseas) probably think it's paradise on earth! If you were to visit, I'd really be scraping the barrel to find enough sights to show you or things to keep you entertained. OK, there's a nice blue harbour, but that's about it! I could spend a week in London and not get bored, a week in Rome is not long enough, a week in Paris and one would barely scratch the surface of that city. A day in Sydney, and you've done it all!
If you did drop by, what would I recommend?
Harbour Bridge Walk
Catch a train and get off at Milsons Point (Northern side of the Bridge). Walk across the Harbour Bridge. Cost, the train fare, time 1 hour.
You've arrived on the other side, take a stroll round the Rocks. This is the birthplace of Sydney, the Old Town. Cost free (maybe buy a coffee), time 1 hour
Walk east around Circular Quay, over to the Opera House. Take your camera out! Maybe go on the Essential Tour. Book online its cheaper $29, 1 hour
Walk back to Circular Quay and buy a return ferry trip to Manly. Cost $13, it's a 30 minute trip each way.
Lunch in Manly
Buy yourself a packet of fish and chips (throw in some shrimps, calamari and mussels too), sit at a bench on the Corso, feeding yourself and the seagulls. Food and drink, less than $20, u.v. rays - free (hope you remembered the sunnies and zinc cream).
Back to the City
Zoos, aquariums are pretty much standard fare all over the world so I wouldn't recommend visiting them. If you've got transport visit the Koala Park at West Pennant Hills. This is the one where you get to pat and feed the roos, maybe even cuddle a Koala. Entry fee is $19. The cost of a taxi ride is exorbitant!
If you can't make it there, the next best is Wildlife World at Darling Harbour. Entry $32. You get to see the weird and wonderful creatures of Australia. You can while away a couple of hours in there.
Finally, Sydney's own Eiffel Tower, Centerpoint. For $25, you get a 360º view of Sydney from 260m up.
Finally, Opera and Dinner
Hope you've booked in advance. Book an opera online and a table at the Bennelong. Chef Guillaume Brahimi is brilliant! Time, the rest of the evening, cost - breathtaking! But then you wouldn't do it too often ($105 - $270 for one opera ticket, dinner hmm...)
So here it is, Sydney in 24 hours!