Amsterdam is about 11 times smaller than Riyadh.

Riyadh (map shows its 9 named neighbourhoods; the area covers the whole city) is approximately 1,798 sq km, while Amsterdam is approximately 166 sq km, making Amsterdam 9.22% the size of Riyadh.
Tip: This to-scale comparison of Riyadh vs. Amsterdam uses the Mercator projection, which distorts the size of regions near the poles.
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