Sydney is about 11 times bigger than Detroit.

Detroit (map shows its 92 named neighbourhoods; the area covers the whole city) is approximately 359 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 960% larger than Detroit.
Tip: This to-scale comparison of Detroit vs. Sydney uses the Mercator projection, which distorts the size of regions near the poles.
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