Rockville is about 15 times smaller than Warsaw.

Warsaw is approximately 517 sq km, while Rockville (map shows its 87 named neighbourhoods; the area covers the whole city) is approximately 35 sq km, making Rockville 6.79% the size of Warsaw.
Tip: This to-scale comparison of Warsaw vs. Rockville uses the Mercator projection, which distorts the size of regions near the poles.
Our free app, MapSize by MyLifeElsewhere — compare any two places, to scale on your mobile device.