Melbourne is about 2.2 times bigger than Riyadh.

Riyadh (map shows its 9 named neighbourhoods; the area covers the whole city) is approximately 1,798 sq km, while Melbourne (the 27 councils of metropolitan Melbourne, without the Yarra Ranges, Cardinia, Mornington Peninsula and Nillumbik) is approximately 3,915 sq km, making Melbourne 118% larger than Riyadh.
Tip: This to-scale comparison of Riyadh vs. Melbourne uses the Mercator projection, which distorts the size of regions near the poles.
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