Riyadh is about 3.8 times smaller than Ho Chi Minh City.

Ho Chi Minh City is approximately 6,773 sq km, while Riyadh (map shows its 9 named neighbourhoods; the area covers the whole city) is approximately 1,798 sq km, making Riyadh 26.55% the size of Ho Chi Minh City.
Tip: This to-scale comparison of Ho Chi Minh City vs. Riyadh uses the Mercator projection, which distorts the size of regions near the poles.
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