Sydney Tower (formerly Centrepoint Tower, AMP Tower, Westfield Tower) rises 309 m (1,014 ft) above the CBD—tallest structure in Sydney, second-tallest observation tower in the Southern Hemisphere. But it's not the overall titleholder.
Burj Khalifa, Dubai, UAE – 828 m (2,717 ft). Though Dubai sits at 25°N (Northern Hemisphere), the Burj Khalifa is frequently—but incorrectly—cited in Southern Hemisphere lists due to confusion with the hemisphere concept. The true Southern Hemisphere champion is:
Sydney Tower's tourist marketing once claimed "tallest in the Southern Hemisphere" before Jakarta's boom. Always check the latitude, not just the country.