Sydney is about 10 times bigger than Las Vegas.

Las Vegas (map shows its 26 named neighbourhoods; the area covers the whole city) is approximately 367 sq km, while Sydney (the 30 councils of metropolitan Sydney, without the Blue Mountains, Hawkesbury, Wollondilly and the Central Coast) is approximately 3,810 sq km, making Sydney 937% larger than Las Vegas.
Tip: This to-scale comparison of Las Vegas vs. Sydney uses the Mercator projection, which distorts the size of regions near the poles.
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