Holy See (Vatican City) is about 402 times smaller than District of Columbia.

District of Columbia is approximately 177 sq km, while Holy See (Vatican City) is approximately 0 sq km, making Holy See (Vatican City) 0.25% the size of District of Columbia. Meanwhile, the population of District of Columbia is ~601,723 people (600,723 fewer people live in Holy See (Vatican City)).
Tip: This to-scale comparison of District of Columbia vs. Holy See (Vatican City) uses the Mercator projection, which distorts the size of regions near the poles.