San Antonio is about 2.1 times bigger than Tokyo.

Tokyo is approximately 619 sq km, while San Antonio (map shows its 401 named neighbourhoods; the area covers the whole city) is approximately 1,292 sq km, making San Antonio 109% larger than Tokyo.
Tip: This to-scale comparison of Tokyo vs. San Antonio uses the Mercator projection, which distorts the size of regions near the poles.
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